Aurapharm sells the GSK - XL version, 150mg, 30 tabs for $32 which I know is a very good price. I haven't been able to locate anyone selling brand name SR version.
Wow, I'll say that's a good price. Drugstore.com, which is representative of the American price for uninsured people, is $231 for the same thing. I guess uninsured Americans will just have to be depressed...
I saw the branded Wellbutrin SR at Candadrugs.com. Drugstore.com charges $230 for 60 tabs of 150mg SR, which saves you one buck over XL, as you need to take SR twice a day, but XL once. Interesting pricing structure there.
I don't know if either of those would ship to the UK.