found a supplier last week, or whenever, in the West Mids, clothesline.co.uk; they do a few garments, but the one i was interested in was the MUW08 all-in-one underwear. you have to phone them and they're mainly geared to the business buyer, not retail, but they will sell retail.
unfortunately, they don't stock the garment in a 'small' and P&P amounts to £10 (for orders under £100).
naturally, i didn't buy, but worth a try if you've got some spare money.
and if anybody knows where i can purchase the same garment, in small or kids sizes, in the UK, i'd be thankful to know. ta.