I have the very same problem - can't afford repairs or new fridge so need to have a go myself. Do you mean the internal back panel in the fridge or freezer? Or is it an external back panel? Idon't want to make things worse - my freezer bit is still working.

Debs, July 2012

Opened the freezer door, took the shelves out and took out the back panels - a couple of the screws that are hidden down a tube like set up took a bit of unscrewing and then because of the ice behind it the second panel took a bit of wriggling around to get it free. Once removed yes there was a big block of ice. Attacked it with the hair dryer - took almost an hour to melt it all. Put everything back together then switched on fridge and it came on and switched off. Turned dials at top to off switched off at mains switched on again and then turned the setting up to medium. Took a good 10 minutes for fridge to get going again but eventually it did and fridge is now getting cold again. Wonderful and the wife's happy too.

Clive, March 2017