champagne gets my vote or something from White Company, Moulton Brown or the other lovely one in our high street whose name has totally escaped me as it is late and i am getting old. Alterntively I received a thank you gift last week it was Posh breadsticks/pates/bisuits etc I thought that was a really nice and thoughtful idea.
I think a box of Jo Malone votive candles or a Space NK gift set would be better than chocs or champagne.
Alternatively a voucher for a spa treatment would be discreet and very welcome, I imagine
I would question why you need to be discreet - surely an input like this deserves to be celebrated openly? Celebrating success is an important part of creating good teams - I'm not fond of the idea that we keep our thank you's private!
Ive never used Jo Malone but just found a beautiful "Start Set" that contains small bottles of fragrances, bath oils and shower gel and cremes - what do you think - £30 http://www.jomalone.co.uk/site.nsf/shop/giftsresults?openform&oc=thankyou&pr=050&rc=Female