Claiming back VAT from EU countries

LynWest

I have a client who is going to be hitting the threshold for VAT in the next couple or three months, so we are looking at registering him. He knows that he can claim the VAT on stock purchased in the UK prior to registration if he still holds it. However, he has bought a lot of his stock from Germany, Czech Republic and Denmark. He wanted to know how easy it would be to go back and claim the VAT back on this. He is worried that he is going to loose margin on the stock from these countries that he already holds if he cannot claim the VAT back.

I don't have any clients that have been in this position so wandered if anyone had any experience of this please?