To get a Brompton for less than 460€ is close to impossible, at least if you prefer to buy a bike that is a) not stolen b) in working condition w/o major defects and c) not antique (with consequences for the quality of the components). This counts for the uk as well as for other countries. And for obvious reasons I'd assume it is even harder if you want to buy the bike remotely.

Here in Germany you can get a very old model (20+ years) in good shape for 500€ish, but only rarely. Also very rarely you can get a relatively new model (~2010) for around 500€ but these are pretty beaten up and in need for instant serious and expensive repairs and maintenance (which realistically add to the price). Both not the best buy if you ask me because if you take the cost of repairs into account and/or the retrofit of some newer parts you can get a newer/better bike in decent condition w/o paying more and save the stress. So this is the better deal most of the time. The problem with cheap(er) bikes from the uk is they have often been used heavily and maintained poorly and to judge on the condition from pictures is not easy. I'd recommend to save a little more - for about 600-800€ you should w/o problems be able to get a proper used bike in acceptable condition in the uk. Which typically is cheaper in the end than an initially cheaper bike.