wheres the best place and cheapest? ive found em at around £100 so far

Depends what size & quality your looking for.

PC World were doing a cracking Hitatchi (IIRC) 320GB external HDD for £114.

Maplin also do good deals on them now and then.

ebuyer
dabs.com
bigpockets.co.uk

those are what i use

Do you mean removable - as in slots into a carrier in a front drive bay - or external- as in enclosed in a case which connects to the PC via USB/firewire cable- or remote - as in attached to your network router to be accessed by any pc in your house?
Removable - any hdd will do*, Dabs have an 80g Samsung for £37 and you can pick up a carrier for about £10 at the next RedRat fair.
External - Again, I'd buy an external case and fit my own choice of HDD into it.
Remote - (choice1) PCWorld have a Buffalo 160Gb NAS with room for a second HDD to be added inside and it includes a USB print server. (choice2) Get an external HDD as above, then buy a NAS adaptor like this (http://www.costcentral.com/proddetail/D_Link_DNS_120/DNS120/E41684/).

*correction - almost any hdd will do, some carriers need a half-height drive, though you should be able to get one for a similar price.

ebuyer, aria, dabs google is your friend.

thanks guys ended up picking one up from pcworld 70£