[Closed] Starter bike/advice on where to go

I found this on google looking up something totally different but saw some pictures and cool looking bikes.

I ride motorcycles offroad and I've been mountain biking a few times in Switzerland.. like on mountains not just down the road. I had a hardrock but it got stolen and I didn't replace it. I like the looks of these bikes that have one gear, like just two sprockets for example [url= ]this[/url] one, the simplicity seems appealing.

So can anyone recommend a decent bike, around £450, second hand no problem, and I'm about 6ft 3. Presume with some know how you can convert a geared bike to a one gear bike pretty easily? I liked the hardrock, it fit me well and was pretty low cost at the time so may get another but nice to have some opinions.

edit -Found the trail guide so can forget that bit!-

I searched before I made this for beginner and stuff like that but didn't find anything really.

Cheers.