Did you ever get to the bottom of this Andrew? Mine stopped working today though a sharp bang with a clenched fist on the box got it going again..so hopefully just a dodgy connection. My mechanic is going to have a look at it next week and he has Maria's number just in case
On a more positive note it passed the MOT with an advisory "Central Exhaust has a minor leak of exhaust gases"....I think it sounds better like that so not too fussed at the moment