Thanks for all the replies

- I've done some googling since and seen that its not an uncommon problem.
Called JL on Wednesday, they (or one of their contracted engineers) are coming out on Monday to take a look at the TV. Strangley when I asked if it was a common problem they claimed they had never heard of it before
Ideally I would like them to replace the panel. I dont think I would be happy if they try to fob me off with one of the Samsungs as I specifically chose Panasonic over the Sammys when I got the PX70 - better blacks and colours (to my eye at least). Having said that perhaps the difference in quality has changed in the last year and half - are the Samsung mondels
gjh mentions any good? Time for more googling I think...
BTW, the JL customer service bloke said if they need to take the TV away for repair they would leave a like-for-like loaner. Which was nice...