I've just bought one of these for charging my phone when out and about playing Ingress.
£10 more than your budget but a great little gadget.
Put it towards an aeropress? chromecast? Gamble it on the grand national
Treat your self to a nice expensive lunch!
Some bits for my Arduino.
20 Rothmans and a cat.
On arrival however it had turned into a gastro pub since our last visit with prices to match! The food was excellent though :)
I actually own one of these exact batteries. First one had a bit of a failure (it would only charge to halfway after a few uses) but the guys offered me a free one as compensation, so if you have any problems, leave them a 2-or-3* review mentioning your issues ;)
Even at only half charge it was brilliant, though. Definitely a nice little pack if you find yourself needing power a lot.
For you.... probably a new coffee maker... I fear the condition of the current one :D
Don't own one, but with both 1Amp and 2Amp outputs, I suspect it would be, actually. Good thinking!
But there you go :D With your £20, but a Pi. Then buy a portable battery. And them some kind of screen. And input.
Oo-err this is starting to cost a bit more than £20..
I'd buy (if I didn't have one already) this:
Bigtrak Junior | Maplin