Point one:
It usually costs far more to buy cartridges that contain all of the colours in a single unit than buying separate cartridges for each colour (particularly if you use 'compatible' cartridges). So it's worth spending a little more to get a printer that uses separate cartridges for each colour as you'll make big savings in the long run.
Point two:
The technical press frequently review all-in-one printers and it's nearly always a Canon model that comes out as their 'best buy'.
With those two points in mind, this is what I'd recommend:
http://www.pcworld.co.uk/gbuk/printers-ink/printers-scanners/all-in-one-printers/canon-pixma-mg6450-all-in-one-wireless-inkjet-printer-21732476-pdt.html#cat-0
If you buy your ink from here you can get a full set of all 5 cartridges for about £16 or, better, get 4 full sets of 5 cartridges for about £50. (So that's just £2.50 per cartridge):
http://www.inkredible.co.uk/inkredible-saver-canon-pixma-mg6450-ink-cartridges
NB: Those suggestions aren't just the result of a bit of googling. That printer is very similar to the (now discontinued) Canon printer that I own and love; the ink supplier is the one I use myself and can highly recommend.