A woman writes: unless she already frequently wears saucy underwear, don't get her that for Xmas (or vouchers towards it). If women wanted to wear fruity pants they'd already be doing it, and you might hurt her feelings by insinuating that you don't approve of what she wears now.
It is hard to know what to buy for women who don't seem to need much. Here are a few generic suggestions under the £50 bracket:
Body Shop tubs of body butter are good - they're about £10, they smell lovely and are extremely good moisturisers/emollients. I don't know many women who don't use moisturiser on at least some part of their anatomy occasionally.
I know it's a slightly lazy choice but I think really posh chocolates go down well with most women. Push the boat out and get some Valrhona/Godiva chocs from a posh dept store (about £10 per 100g), it'll cost a metric arm and leg but wins major brownie points. Plus, you'll probably get offered some, bonus!
John Lewis are doing a big range of leather gloves (£18 a pair) in all colours of the rainbow made from very soft leather, those would be good if she has a colour she particularly likes and likes to dress smartly at least sometimes.
Decent headphones for her iPod - if she's using the ones that come with it, they're crap. Bose and Sony both do really decent in-ear headphones (£30-40).
DAB mini/portable radio, so she can listen to Adam and Joe on the move on Saturday mornings (£40)
If she likes cooking and food, there are all sorts of cookbooks out there that she might enjoy leafing through - many these days are half novel/biography, half recipes. Nigel Slater has a new-ish one about vegetables (growing and cooking with them, £20 list price but cheaper online), Heston Blumenthal's Fat Duck book is just bonkers (£30 list price, cheaper online). Martha Stewart's cupcake book (if you buy a set of cup measures to go with it, £15 list price but cheaper online) is a good choice for the very nicest cupcakes, if she's remotely interested in the cupcake bandwagon. Note: cookbooks BAD idea if she thinks cooking is a boring chore. Then, they're right up there with ironing-board covers.