Trek girls bike 20" wheel (5>8years) £129.99 inc del +3% quidco @ Rutland Cycling

seems a lot for a bike that wont last long. I am not doubting durability but kids grow so quick.

True but if you have a little one like ours who rides every day then its money well spent. Ours has just outgrown the smaller version and its still mechanically spot on. The coaster brake in the hub is a great feature that saves the little ones from grabbing a load of front brake and chinning the floor(and still works when wet).......you just have to apply pressure on the pedals in the opposite direction to make it work.