In reply to abr1966:
At that price and second hand it will be a lottery - if you buy a duffer (e.g forks, rear shock or bearings gone or need servicing), then you could be straight in for spending £££.
But, a mountain bike (if you do a fair bit, especially in gritty areas like the Peak in winter), is just a case of constantly throwing money at it anyway, so expect to have to spend dosh once you get one.
If you have experienced MTB matres, best bet it to wait for one of them to upgrade... or get them to find one locally on Ebay and get them to check it out for you.
At 5.11, you are probably a typical MTB L frame, but some M might be OK.