Rough cost to replace window sills and generally sort out front of house?

[AllTheShoes]

I'm in London, and we've just moved in to a terraced house where the front clearly needs a lot of work. At the least, some window sills are rotten and need replacing, plus all of it needs painting, gutters sorting, maybe some sort of waterproofing on a damp bit of wall (though perhaps sorting out the gutters will deal with that).

Anyway, what sort of cost am I looking at? And is it job for a window specialist, a general builder or what? My handyman says it's too big a job for him as the wall is load-bearing and he's not up for dealing with supporting it while he takes out the rotten window sills and replaces them.