That's the bit you need to look into if you are still sending out quotes with no return do you ask them why.
How do you know, as in above, if you don't ask, are you VAT registered?
That is a very narrow field of scope, If I relied on "interiors" for all my work I would be out of business its too competitive and many DIYer's tackle them themselves, perhaps people are looking at your quotes just as a guide for themselves to build.
My experience has proved to me it isn't worth getting involved in low budget projects for the return, I have just fitted a £4k Wickes kitchen, we knew we wouldn't get anywhere close on a price, another pal of mine is having a Howdens kitchen that I will fit, again cost driven, and my Mum has just had a 4 door wardrobe with 2 draws, supplied and fitted all for £500.00. All these are evidence that this level of market value is pointless.
I have said this in the past and is my standard approach on new enquiries, ask them how much is the budget, saves an awful lot of wasted time and disappointment, I had one recently to make 2 Oak gates, quite complicated, budget was £1K, a quick price for the raw timber was £600.00, I did offer to do them for £2K, but never had a hope.
Perhaps an avenue to explore is doing Kitchen fitting as well as the option for making.
I am very fortunate I have £0 liabilities so if I do nothing I can still survive, my work scope is very varied but principally based on Joinery, whist not excluding other options as well, and more so working on projects that are long term, at this time I have enough work to see me through to well into next year, which in itself can be an issue as people don't wait for long, but that's not my worry.
My other benefit is my workshop facilities, are cheap to rent @ £200.00/month
Have you seen Alastair Johnson's company
Freebird Interiors, he has some useful
Utube vids on setting up his company.