Hi guys, just thought I'd comment that I have just been able to get a full node running on a Raspberry Pi Zero W, with a 1TB external hard drive. Here's the tutorial I followed, if anyone else is interested. http://raspnode.com/diyBitcoin.html

Cost: £37 for Raspberry Pi Zero W – Mega Kit with Zebra case + 1TB hard drive I had laying around (probably bought it for about £50 at some stage).

Could be done much cheaper, but since I wasn't sure it would work for a bitcoin node, I got the mega kit and case in the event that I'd end up using it for something else.