I've had EU sellers just chuck the package in the post, no declaration, nothing and it arrives no problem, no fees. It's upto the individual seller how they do this obviously but I don't see what the UK customs can do about it if they just ignore their stupid bl00dy rules!!
The process the UK revenue & customs want global sellers to adopt is, the seller must register for a UK VAT account to sell to the UK and the MINIMUM order value must be £135!!! Why TF they impose a minimum value is beyond me, but that's the way it is. I first encountered this with a US seller whose system rejected my online order when it detected a UK destination. I didn't know about all this b0ll0x at the time so I emailed to ask why my order was rejected, which is when they told me about the issue. They said they now don't ship to the UK as the cost of administering a UK VAT account just wasn't worth the hassle. What an utter cluster fcuk!! I'm a Brexiteer and this has annoyed me intensely!! This UK government claiming to be all for international business then coming up with this utter drivel!!
However, as I mentioned some sellers are sticking up the royal salute to it and just sending the goods!!