Highly recommend a pair of these.

Very comfy and extremely durable. An excellent all round off road trainer (even cope with those roads to the fellside without worrying about wear). They cope with most terrain admirably though the studs aren't deep enough to be suited to steep wet/muddy descents at race speeds.

Depends just how heavy you are with your tyres, but one pair (I'm on my third pair) should get you around a full year's worth of training at around 30-35 miles per week. That's very good mileage! In my case, the uppers out last the sole which I don’t think I’ve ever had with any other trainer (e.g. either my tootsies break through, or they simply start separating from the sole).

You can get them for £37 at Sports Direct if you choose the less popular colour schemes.