Try click here for prices for printers. Got a Canon 950 myself and the ink isn't too expensive, with the added advantage of being individual cartridges. click here are normally pretty cheap for offical consumables.
Depends what you want it for, if it is for photo printing, I have seen results from the 915 and it is difficult to see the difference between them and real photo's. I have an Epson 895 (one before the 915) the only difference between the two printers is the 895 only comes with one camera card adapter, but the 915 comes with all camera card adapters. The 830 and 900 (as far as I know, do not have card adapters, but I think they all print borderless prints. All my ink is bought from Choice Stationery at click here
I just got the epson 900 £99.99 down from £149.99 in Curry's/Pc World/Dixons. It is top quality and can print directly onto CD's, photo pictures are amazing, you wouldntknow it was digital. I actually read a review in a mag yesterday and they said it can do all the 915 can but for half the price.