When it comes to breaking down the kebab for the build can I use the power assisted brakes, a la Robin Hood, or would I just need to use normal brakes?

I would suspect technically that I could use power assisted, but would there a) be enough room in a convenient place to fit that bit ugly servo and would it be a bit too agressive for braking.

I wouldn't bother myself. You don't need it.

Yeah I thoguht they my be a bit overkill.

I'm getting into reading the haynes book of lies at the moment. Am I right in assuming the servo gubbins is just a retrofit onto the standard braking system, i.e take the servo bits off / bypass them, or do I need something like a new master cylinder?

The servo bolts on to the master cylinder, and should be removable. This'll leave a nice (poss) shiny master cylinder for your use.

I have a booster on my car. It works very well and provides smooth, subtle and very effective brakes.

I did have trouble fitting it low on the end of the drivers footwell but I don't regret doing it at all.

Please be careful when removing the servo unit. Sat inside is a spring waiting to take a chunk out off your face. Where gloves, protective face visor if performing this task, or better still by a buy new master cylinder.
Cheers Nige