Another site was waking on about a red drive belt for Rega TT's . . . only £8? . . . worth a try. Arrived today, fitted it, over size, to slack and it felt a little more forgiving in stretch mode that my excellent, 'Edwards Audio Little Belter blue belt' that I found out performed the Rega white belt.
However, the platter and belt removal prompted the cleaning of the belt/motor pulley/sub-platter drive chain. These have not been cleaned properly for 6 months, so I swabbed them with Isopropenol . . . made a surprising difference, sharpen things up, better leading edges to transients, base flowed better and one was more aware of inner detail. A small bottle of Isoprop and a more regular cleaning regime is in order, very cheap to keep on top of things . . . by the way, Edwards Little Belter blue belts (available from Deco Audio) are cheaper than white belts.