How can I fix my hotpoint fridge/freezer?

Hotpoint fridge/freezer FF187L. Three years old.

OK for first two years then warning lights came on and fridge was 10-12 degrees and freezer was only -3 degrees. Two year insurance had just finished so reinsured M/c (£96 and called in for repair, first thing engineer said was 'I know the problem, common with this model', the frost free freezer had frozen up.

Removed all contents, removed back inside panel of freezer compartment and proceeded to defrost freezer pipes, covered with frozen ice with an hair dryer. When free of ice, replaced back panel and said it was OK.

One year later, just three days after the insurance cover ended the same thing happened again. This time I removed back panel (only 5 screws) and defrosted frozen pipes myself. This time it lasted for only six weeks before it happened again. Did same again and four weeks later same again. This lasted only two weeks before same problem reapeared.

The other frightening aspect is that when the freezer is on the middle section of the front sidewalls of the freezer compartment, either side of the door get 'very hot'. How far back this heat goes is very difficult to judge as the freezer as cabinets either side.

Contacted Hotpoint but all they will offer is for me to pay nearly £200 to reinsure M/c to send someone else.
Obviously I'm afraid this is pouring my money down the drain.
Any sugestions?

The M/c comes with a five years parts gaurantee but you still have to pay through the nose to activate it.