Aside for the marvellous suggestions above...

Ebay too, mostly. Just bought another pair of gloves this morning, in fact.

Asda has been doing some pretty lingerie recently, always worth a nose as you're going past. Their range goes to some most respectable sizes.

The Online Hosiery Store - Stockings Direct - for plus-size seamed tights and stockings, or the tights stall on Brum bullring market.