Hi Richy
Nice little job there matey!
The upvc is going to be a pain... even if you get rid of the paint, the chances of it being stained by the pigment in the paint are massive and you will probably have to replace anyway. If I were you, I would just get a quote for replacing the upvc and stick 20% on top (I am assuming it is an insurance job).
It probably won't be financially viable to clean it is what I am tring to say I guess.
The blocks and roof etc, charge them somewhere in the region of £750 a day plus VAT if you are registered... you will have to judge how many days it is going to take as I can't see the extent of the damage.
I do loads of insurance work and basically, as long as you keep the cost of cleaning something to lower than replacement, then they will normally go for it. For example, £1500 to clean a roof is worth it for them otherwise they are going to spend £5k on replacing it.
If you use steam to remove the paint and then some ghost remover to remove the last traces of pigment you shouel be able to clean a whole house, roof and all in a couple of days.
Hope this makes some sense.
Andy