You generally get what you pay for, so assuming you're going for 19's, anything around the £900+ mark for rims only should be fine.
BBS, OZ and Rays are all premium brands and will also be pretty light as well as strong. Rota's will weigh a little more, about the same as OEM wheels, but at about 40% of the price of the other 3 and are highly regarded across all forums i've seen.