You also might miss out on a worth while deal for the bass you're looking for if the forum is split by UK/Non-UK.
I've seen basses in the UK being offered at say £1000 and the same bass being offered by someone in the EU at say £700, so you're still potentially able to get a better deal even with tax included. Also depends of how 'ready' the seller is to sell, someone in the UK might be hard on price, someone in the EU might be flexible.