D'OH. After posting on here, researching the price for a new power supply, and even ringing a repair centre help line, I finally discovered it was all because I hadn't put the bottom door in place. Everything works fine now, and I'm enjoying my new bandit. And all for the princely sum of 30 quid. Thanks to everyone's postings.
Is there a way I can check the power supply, or is there any other signs that may be going on that the power supply is failing?
There are no error messages anywhere and everything else seems to work fine.