doubt they'd send 31s from derby because a 153 broke down, i know a couple of times ive seen a 158 failed at Westbury (31s were at westbury that time) and once was just cancelled (have to get next service out) or a 158 replacement
Still dunno if Greater western will use them, in the NRT i see the summer Warminster - Weymouth still runs and was a 31, still might only be a 150 + 153 combo or something, but hey what am i moaning at! Wessex 31s arent too great, i think its down to the driver, 31602 at the SVR was some real clag and noise!!