I have just spotted the battery grip for my 400D (as bought from tesco after seeing on here ;-) ) and see that it is 1/2 price in comet! this is normally £129.99 and at very best can be had for about £90-100 on the high street. I know that these can be bought on Ebay for about £70 + delivery from HK which carries the risk of import duties...
Reason: The battery grip has been flagged by Comet as end of life (has a D after the product code). I imagine that they have this linked as an accesory to the 350D camera and are blissfully unaware that it also fits the 400D :-)
My store here in sunny Swindon only had one in stock so it may be worth calling first.