Re: @Nick Kew
Or how about, take your existing 'fridge.
10l water carrier with tap £10
small float valve £6.40
a self-cutting isolating valve £5 (tidier methods are available)
a short length of flexible pipe and necessary inserts £2.10 & £3.20
a flat wood bit £3 (it'll get through the plastic lining and the insulation easily, and the external metal is thin enough that it should manage one hole - many fridges don't have metal at the back but you will have to be careful to avoid the radiators)
and a short flexible tap connector
Seal the hole with silicone when you're done (wouldn't advise expanding foam) and Bob's yer uncle for around £30.
I'm tempted to try it myself. Not sure how the rest of the family will take to me drilling holes in the side of our fridge though...
M.