Mountain Biking Glentress

Which mountain bike for around £300?
I have around £300 to spend on a mountain bike. I intend to use the bike for general transport as well as trips to downhill MTB courses (like Glentress, Peebles).
I would like full suspension, quickfire gear shift and disc brakes. What bike would you recomend? New or Second Hand considered.
I have just bought a Trek hybrid. I know it is not a mountain bike, but Trek is a very good make and I love the bike. My mate has a GT mountain bike with quick fire and disk brakes – it was £320 I think. This was recommended by a mountain bike magazine from 4 others around the same price. One point is that disk brakes wear out VERY quickly. My mates needed changing afte 1 1/2 hours hard riding.
P.S. you can get an entry level hardtail trek for around £270.00 – http://www.trekbike.co.uk/2007/bikes.php?sec=overview&MainCatID=2&SubCatID=8&RangeID=0&ID=210#
Mountain Biking – Glentress Freeride Area

