This project is determined to drive me mad..

Seeing that you are on a roll, I have another question if you don't mind.

Testing was going well until the circuit stopped working all together. On checking the PIC was getting power etc so I tried reflowing the solder on a few points and it started working again. It would work for a few minutes out say 5-10 minutes later I would power on and nothing. This appears to be repeatable, could the 22pf caps or 4Mhz Oscillator be working due to the heat caused by resoldering? I only ask that because there doesn't appear to be anything wrong with solder joints, so I wondered if it is the heat that is causing the circuit to work? I'm going to try swapping out those components and see what happens.