Well whilst I await the receipt in the post I managed to track down the mastercode and have used the tv today.
Had a strange one and now can't use it....
The tv was in aux mode watching freesat. The room temp is fine (if that's relevant) but the tv suddenly went into standby (curtains closed and swivelled into rest position in the middle of watching it). No idea why. But worried its a problem. Then when I pressed tv it asked me for pincode. I thought pin was cancelled etc so I tried the mastercode I used this am (ie left arrow held down etc). It won't accept this as the mastercode now...! Bizarre, feels like there is a fault?
Any thoughts welcomed!!