I don't think there'll be any extra costs from Thomann themselves - the website price will include VAT and handling, so it should be the price you pay: nothing else. But they're not there yet!
I've ordered a product at £216 pre VAT and handling, and I reckon it's going to be £274.72, as against the old potential price of £256.80 (i.e purchase price including VAT), which means the additional handling fee will effectively be £17.92. That's not exactly earthshaking - perhaps we can call it the price of Brexit (no trolling intended!). Certainly manageable, given that I can't get the product anywhere else and - even if I could - it would probably be more expensive.
But I was never great at maths!