I previously posted why China was a bad idea for metals, but let's consider a few points against the UK:
1) It's the UK
2) There is a non-zero chance that whoever choses to do business with you will end up on a fucking watch list or get public flak. Someone will rat us out; they always do. If you get someone who doesn't care or is blissfully ignorant, then that might help, but barring that there's a good chance that they might pull out when they get an angry phone call or worse, the fucking fun police (or real police) show up at their door and give them shit that they don't really deserve. I don't like the idea of some small precious metals artisan with like four centuries of history getting shut down because they did business with an Internet Bad Guy. This is not an issue with China because A) unless we put a picture of Tiananmen Tank Man on the obverse or some shit, China don't care and B) fuck china anyway lol.
3) It's likely going to cost more because it's going to be done right.
4) It's the UK and the silver is going to smell like baked beans and a chippy or some shit.
So yeah. China there's a risk of not getting the right goods, but the UK there's the risk of saddling an otherwise innocent company with the patented "KF" scarlet letters.