I'd go for Ketel over Grey Goose, but both are good.
Snow Queen - just around budget
http://www.farehamwinecellar.co.uk/0/582eb3730c92637d802572230049b012.html
http://www.thedrinkshop.com/products/nlpdetail.php?prodid=2682&afwinid=90909
Ciroc Vodka, uniquely distilled with Grapes. Super vofka. £10 over budget though
That is not vodka. That is a grape spirit of some sort.
I'll second this. Only had it a couple of times but it's the only vodka i'll drink