I'd like to add a couple of points to the above - NOT about taxation (VAT/non-VAT), customs duties, and shipping charges (preferential or not). Because I agree with the points above - "unknown at present" - a lot will depend on what's finally negotiated in various trade agreements between the UK, the EU, and other "3rd party" countries.
But what concerns me as someone who lives in a non-EU country is the "willingness" of suppliers in the EU to supply to customers in non-EU countries.
A few examples as illustration - 1st, my wife wanted to buy a silk scarf as a present for someone a few years back. Amazon in Germany would NOT supply to a Swiss address. Neither would Amazon UK. Amazing? Well as there is no Amazon in Switzerland, I thought it was, at the least "surprising". In the end she bought exactly the same thing, on line from China.
2nd, again my wife, who wanted to buy a carry case for some electrical gear. Made in Germany and costing about €18.00 (as per the manufacturer's own leaflet, included within the box the gear came in). Case available in Switzerland but costing CHF 60 (more than 3 times the price). Neither Amazon Germany would supply direct, nor the (German) manufacturer would supply to our Swiss address (although they have an on line sales web site). Could only solved that problem by getting them to deliver to my wife's girlfriend in Germany who then brought it with her on her next visit.
3rd, I bought an oscillating band/drum sander last year. LOTS of different suppliers on line in Germany and UK (the machine is badged with various "German" and other tool brands but seems to be actually produced by at least one OEM in China). Several suppliers in Germany listed the product (with those different badges) including Amazon Germany, who were one of the cheapest. Just about all the German prices were lower than UK prices. But several, including Amazon Germany would not supply to a Swiss address. In the end, I found another German "badge engineer" supplier who would supply - not the cheapest, but price "OK". So deal done. (Useful machine for me BTW).
4th, a few years back I bought a Record Power AC 400 air cleaner for my shop. Record wouldn't supply direct, but pointed me to their Swiss dealer. The Swiss price was nearly half as much again as a German Record dealer I found on line who DID supply me (and BTW, the German supplier's shipping cost was €20 for approx. 200 Kms, the Swiss dealer's shipping charge was nearly CHF 90 (x4!) for less than a quarter the distance)!
There are several other examples I could quote but I think I've made my (various) point7s.
AND I can't actually prove it, but I have the feeling that instances such as the above have been increasing over the last few years.
What is NOT clear to me is if these suppliers are driven by their own internal company policies or by "Govt" Regs. If the latter, which Govt, theirs or "mine"? And how come some suppliers in a particular country WILL actually supply the same goods while others in that same country simply wont?
I do not pretend to know the answers to any of these questions, but like me, and for another example, as member sunnybob living in Cyprus has already found, at least sometimes he, like me in Switzerland, has had to resort to suppliers sending to an address that IS "allowed" and then making personal arrangements to get the goods onwards to where they actually need to be.
I am NOT trying to be a prophet of doom and gloom here, nor am I particularly pro- or anti-Brexit. That's a done deal now anyway. And as above, I have NO idea what's going to happen in the future to ANY of all this.
All I am trying to say is that I suspect that any UK-based member who wants to import tools (or many other things) from anywhere "overseas" is in future in for a bit of surprise and quite a lot of frustration.
And I have absolutely NO idea how the future will be for heimlaga in Finland. Good luck mate!