When I first got my sky+ is would freeze at least once a week and only
reset if the power was removed.

About a year ago, I aquired a UPS and fitted it the to sky box as it has
a hard drive and it has been perfect ever since and never needed to
reset it at all.

The UPS has a power surge protector built in and also, the voltage to the
box is constant.
Also it has a phone line surge protector too.

* UPS = Uninteruptible Power Supply *