If you're looking for a cheap, cheerful, and small Android phone on a Pay-as-you-go tariff, this offer is fairly good going. It's also the best deal around by £10.
Admittedly, the the S3 Mini is somewhat dated now. The camera isn't brilliant, and the Samsung UI and pre-loaded apps might cause annoyance. However, the fact you can put in a MiniSD card is useful, and its small form factor with the Galaxy experience is a plus. Thanks to pmackers @ HUKD!