For the autopilot fix try Lees avionics 01494 513661 or Gatwick avionics at stapleford (make sure that you are talking to the guys at stapleford because the Redhill part of the company do not realy understand this end of the avionics market ) 01708 688064.
There two things that will kill avionics water and heat the posts above have coverd the water contamination but the heat is another matter.
As most avionics buying is price lead the cheapest quote normaly wins and the companys know this and will quote you the rock bottom price for fitting because if they dont they dont get the job !.
However this means that things like avionics cooling have to go by the wayside because the extra £250 to fit a cooling fan will lose them the job.
The atittude among aircraft owners in the UK is that avionics wont get hot enough to need the "expencive" cooling fan , but this course of action is just a money time bomb as over the years the radios suffer the efects of heat buildup and then pack up leaving you with a big repair bill.
It is no coincidence that King put a cooling port on all the radios that they think need cooling.
The avionics fit on my aircraft was done in 1994 and I have had no failures in the cooled kit and only minor transponder problems but this is the only Narco item I have and its low quality shows ,this will be replaced by a King or Garmin unit when the mode S units become avalable later this year.