In the end I bought the TZ-99 from John Lewis, and paid the extra £30 for the extended warranty so at least I have peace of mind for two years !
The TZ-99 slightly bigger (thicker) than the TZ-70 and heavier, mainly due to the fold up screen which I am in two minds about because I am concerned it is a weak point.
It's also got a load of extra feature, too many, which I am not really interested in and make it more complicated to use, plus lacks the "panoramic" function which I did find useful at times.
Lastly it definitely does NOT take the same batteries as a TZ-60 / TZ-70 which is somewhat inconvenient !
Of interest is that Premier Electronic Services quoted £70 for a replacement secondhand display, or £110 for a new one. The thing that put me off is the camera also was exhibiting symptoms of dust in the lens, which was an expensive fault to repair (complete lens strip down £100 to £120, or a new lens at £148).
Later Addition - With experience of the TZ99 I preferred the TZ70.... Not only was it significantly cheaper, it is also a bit smaller, it is simpler (The TZ99 is too complicated with far too many esoteric functions), it had the "Panoramic" function and it had a bit of internal memory (which caught me out the other month when I forgot to put the SD card back in ! ).