Note
Bought a new MTB as old one wasn't worth repairing.
Another 29er, this time with carbon frame and single front chain ring.
For the record, here are some stats on the old bike (AP very useful here):
Date of purchase: 29th Jan 2014.
Mileage: 3,500 (at av speed of 11mph)
Not sure whether this is any good? It's expensive compared with running shoes. It certainly gets some hammer.