Folk or parlour sized steel strung guitar. Expect to pay about £100, anything less than that is likely to be a bit suspect.
That's dh's exact words.
Electric. It's usually cheaper to set yourself up with an accoustic first, to see how you go. With an electric you'll need an amp, headphones, strap to start with. Practise amp is about 25 or 30 quid, Squier do an electric for 100 - vey good quality and playability. Leads etc.