Brompton: where to find the higher supply of second-hand bikes in UK, or anywhere in Europe? We are 2 french hitchhikers looking for 2 second-hands brompton folding bike (M6R, black).

We are ready to hitchhike to get them anywhere in UK, Belgium, NL or Germany for a "reasonable" price. Logically the UK should be the best place. 

We are looking for specific shops name that would have for sure some stock when we will arrive because it will be quite a challenge just to get there (hitch-hiking), and for the same reason nearly impossible to run after private offers (without taking into account the risk of concealment).

Have you seen more than 4 of them in a single spot, in which country, which city? Any advice will be warmly welcomed!

ps: we chose this brand because the size matter a lot for us. We just could not find anything else we could carry on our hitch-hiking trips.
If you'll be in the Netherlands any time soon, many used bikes are sold via www.marktplaats.nl. There are also a lot of addvertisements from shops, including these to:

Advertisement 1

Advertsiement 2

The second one has some 2013 M6R Black bikes.
I don't have experience with these shops. I do often use marktplaats.nl.