On or around Mon, 25 Apr 2005 08:11:26 GMT, snipped-for-privacy@lardrover.co.uk enlightened us thusly:
f*ck orft.
but in all seriousness, the seat frame is poorly designed/made; and also, the seat foam gives up the ghost an' all. Unfortunately, the fabric appears to be built into it, in some way, which rather precludes replacing just the foam part, even if it can be got.