Register for a UK VAT number

[thebluehound]

Hi, I have a small online shop based in the Netherlands.  After Brexit, I discontinued selling to the UK due to the then newly established rules (it was a very small part of my sales).  

I would like to start up again, but am not sure of the VAT process in acquiring a British number and subsequently submitting collected UK VAT to the tax office there.  I've read some things on the UK Gov site but to be honest, it looks quite complicated..maybe I'm mis-reading it.

Does anyone have real life experience in doing this and might be able to provide me with some guidance?  Generally my product is over the 135 threshold and my shippers require that I have a UK VAT .

Also, is it difficult to adapt my Shopify settings to reflect a UK VAT amount?  Currently it extracts the Dutch VAT for non-EU, but I'm assuming that it would have to reflect British VAT for under 135?

Thanks