I bought one of these Merc Bikes on ebay for £330, and I've been riding it around for a few days. I like it a lot, though I think with a fifty two tooth chain ring and a 14 tooth sprocket, it is a bit over geared for the terrain around here. I am used to riding a mountain bike though, so having only three gears takes a little getting used to. I intend to reduce the gearing a bit and have ordered a 44 tooth front chainring at the local bike shop to substitute for the original. This may be an idiosyncracy of my own (I'm 55 years old) and I do regularly need to ride up some steep hills. The bike felt weird at first, but now it's second nature to me and I love it.
It seems nicely finished from a cosmetic point of view, though as delivered it had a jammed gear change cable, which foxed me for a few minutes until I discovered what was wrong. The brakes are a LOT less effective than I'm used to and need a darned good pull to stop you on a hill. This may improve as the rims and shoes wear in. Another minor annoyance is that the seat post seems to slide down gradually, even though I have it clamped pretty tight. The movement is slight, but over say a half and hour, the seat post will sink maybe a half an inch into the frame.
I really like the bike inspite of these minor niggles, it rides amazingly well for such a compact machine, and has all the gadgets you need at a budget price. It comes equipped with lights, dynamo, mudguards, front luggage system, rear rack, carrying bag and a wee pouch to put it in whch will attach under the saddle.
It is such a compact and effective little ride that I think my other bikes will see a lot less use in future. For everyday whizzing about the city it seems hard to beat, and I can easily ride it at twelve to eighteen miles an hour, depending on headwinds, hills and so on.
When I get the smaller chain wheel, I'll bring some feedback about how it works out. Plenty of people on the Brompton discussion sites recommend this change if you happen to live somewhere a bit steep and windy like I do.