Tom,
You, and only you, know how much pain you can handle, what your thresholds and tolerances are and whether you can work at the job you are currently employed in or not. We cannot advise on the original question you posed since we all have different tolerances to pain and two presentations of the same disease are not identical. What we can offer advice on is alternative strategies or thougts for your wider situation. To me you have 3 areas - work, medication and woodworking. Running through these is an issue of finance.
Lets start with work. You state you are an IT consultant, and you appear to have an understanding employer who has stood by you so far. They will not carry you forever however and you have a meeting with them soon to discuss future options. The first thing you need to do is have a plan and some suggestions for that meeting. To show a willingness to work if at all possible. So you need to be able to offer to work part time or flexi time. You need to offer to work from home, or switch roles so you can work from home. You need to show you are trying to help as best you can, while realising that as a company they have a bottom line to protect. The smaller the company the less likely they are to carry you indefinitely, but the more relationships become important and the harder it is to let a friend go. Be positive at the meeting and show willing, as I am sure you will be. In a worst case scenario they have to let you go, start thinking about alternative employment now. You have IT skills, can you do odd jobbing or contract work from home? Can you offer web design services? Can you offer programming services to anyone? Can you set up your own business - IT would seem to have little in the way of overheads and equipment so its feasible to run from where you live.
On to illness and medication - if the pain is so great that you cannot work then you need to seek pain relief from your GP and not take 'NO' for an answer. Change your GP if you have to, or at least seek an appointment with another GP at the same practice, but if the pain is such that you cannot work then it needs medicating. Explain your situation to your GP, about your desire to work, that you do not want to be on benefits and that the pain makes it difficult. Book a double appointment to get the time you need to explain everything. The NHS also offers counselling services if having someone to talk to in confidence outside of family and a public internet forum helps you. Be realistic however, the NHS takes time to do anything and it cannot cure everything. An awful lot of medicine is trial and error and diagnoses are not 100% correct first time. You may well need to play with meds to get the relief you need and you will get different views from different docs. They are not doing it to be deliberately annoying. Going private will get you quicker treatment and a more sympathetic ear, but will not necessarily provide a more accurate diagnosis.
Woodwork - I am going to be brutal here, and apologies if its not what you want to hear, its just my opinion. You need to scale back - big time. As already discussed in this thread, pick an area you can do a bit of and stick with it. Be that turning, box making, scrolling, hand work or whatever. Something that is small scale in terms of size and equipment needs. Make sure its not a chore, something that gives you pleasure, but not something that needs a double garage and 15k worth of kit. So you want to make furniture? No problem with that, but you will still be able to make it in the future provided you are sensible now. Be realistic with yourself - sit down with a blank bit of paper and ask yourself what you want to do, what you need to do it and then temper that with your current finances, your future finances and your desire to support and nurture your family. You very often have good bits of kit for sale on this forum, bought at full price and sold at a loss. Be realistic befoore you buy anything else - is it a requirement for your current needs or is it a luxury? Yes it may be useful for furniture making, but does it pay for itself now in terms of either work saving, time saving or resale value. If the answer to all those is NO then don't buy it - its a desire not a necessity.
As for finance - thats not something that should be discussed on a public forum except in the most general terms. Only you know your incomings and debts and whether those debts are secured or unsecured. You primary aim, if you suspect your income is going to reduce is to reduce your debt burdon as well. This can be something simple like cutting back on expenditure (take away meals, cheaper shopping bill, less going out, less tool purchases, or turning the heating down and putting a jumper on) or something more drastic like selling assets. As you are finding though, resale value of stuff doesn't cover purchase price - as true for tools as it is for cars. If your debt burdon is still so big that you are going to end up defaulting then there are ways to deal with this from Citizens advice, to speaking to creditors directly through to IVA and voluntary insolvency. Noyt all of these are recommended for all circumstances and you definately need to speak to a professional if you are this far in. As to downsizing the house and mortgage, a house is typically your biggest asset. If you have a mortgage on it you can do one of two things - pay more to clear it quicker, or extend the loan period to reduce monthly repayments. Option 1 is usually not feasible, option 2 doesnt tend to save much but can be handy if you need small amounts iof regular cash. It will increase overall debt sthough due to interest payments. To downsize house you can do either of the above, although from your description I presume you are doing it to reduce your mortgage payments and get some equity from your current property. Be aware that you are not a first time buyer so stamp duty still applies, and that to move will cost in the region of 10-15k when you factor in EA fees, stamp duty, solicitor fees, removals and decorating the new place - more if it needs DG windows etc. Above all with finances, don't hide from it as it will not go away - sit down with a piece of paper again, work out what coming in, whats going out and if out is more than in decide how to reduce the out or increase the in.
Sorry if that is a bit 'sucking eggs' and obvious, but sometimes it helps to have the obvious stated. Whatever you do make a plan and make a start on sorting things out - woodwork, although it may bring you the most pleasure, is the least important of the above areas and while you do not have to stop it completely even in a worst case scenario, you do need to be realistic in your priorities.
Best,
Steve