i accidently left my keys in the ignition in the on position for a few days (well 5 actually)
i jump started the car this morning and amazingly my hard to read mileage was perfectly clear for the first time since i've had the car.

Excellent. Can read mileage OK on mine, but the rest of it - pretty jiggered.

Generally, its not the pixels that fail, its the ribbon cable that tells the module whih ones to put on. It goes brittle over time.

Replacement and upgraded ribbons are cheap on the bay of e, but you have to take the cluster out and drill holes.

Not recommended unless you are brave.

A few companies offer a repair service, but then you prob know that already.

Not sure how fiddling with the battery would sort it, but as long as its fixed, job done. 2011 Range Rover Vogue SE 4.4 TDV8

Previous cars :
2003 Range Rover Vogue TD6
1999 Discovery Td5 ES
1995 BMW M5 3.8 6 speed
1992 Range Rover 3.9 Efi Vogue
1992 BMW M5 3.8
1988 BMW 735i SE
1989 Ford Sierra XR4x4 2.9i
1981 Ford Fiesta Supersport

Nice bit of luck, but maybe short lived. Mine work perfectly when it is cold, but soon die as the car warms up, and on a hot day (30+) they just about disappear altogether. I have the new ribbon cables to fix them, but not yet worked up the courage to try them yet...