Ok, just flashed.
The phone rebooted and I was greeted with a nice Vodafone logo! Didn't realise it was Vodafone branded...
Still playing around with it, but have just installed Diagnostics and they've updated the battery status app. It only shows Voltage and Current (ie, full charge capacity has gone). I have to say, it's idling at a MUCH LOWER discharge rate than before. At idle, it's discharging at 50 - 65mA!! On 11501, it idled at 140mA!
Will post with more info after I've had a play around