Just a quick update...
I had Nick's code running fine yesterday, however today when I tried it, it was a no go again. Tried on a couple of different chips and rewired a dozen times so who knows what's going on there.
Went back to the code I'd posted above. The trick is not so much in the detachment of the servo after all that, it is to put a protection diode on the pin controlling the servo .
Testing on my desk at the moment and working fine. Figured this out as there was no current when the red to the servo was detached, but remained current draw when the brown was.
Trick for young players I guess.