Comet has this Lexmark P315 compact photo printer (with 2.5" preview screen and direct printing from your memory card) for £39.95 inc Free delivery
This is the cheapest price I could find for this model. Go through Quidco for a further 3.5% in cashback.
Lexmark P315 description:
With Lexmark's P315, you can print from a variety of memory cards or from any camera that supports the PictBridge standard. This solid-looking, squat little machine – shorter but with about the same footprint as a domestic toaster – sits on a flat, rubber base. There’s a retractable handle on top, so you can transport it easily.