Well home now so had chance to have a closer look.
I dont think its a power issue, not as far as the tartget pic is concerned, it looks like the bus transceivers for dat and clk despite having zeners and thermistors protecting them have fried, and they are pulling down the supply rail withion the pickit.
My usual suppliers dont list the 74lvct45 but RS do, so I'll order some when I'm back to work next week.
The pickit still connects to mplab, you can upload firmare to it and the status leds still work, so the internal pic still seems to be behaving.
If new xceivers dont work then it'll be on its way over to you Nige.
T'other thing is, when 5v for the pic came from the pickit it didnt run properly, with 5v from my relic bench supply it works fine, I think its a ground issue with the 9vac supply.