Hello Baz.
The truth is, I really hate commenting on someone else's price. Especially as he's seen the job and I haven't.
First off... is there VAT included (over 60 pounds)?
I'll assume it isn't (he's not registered.)
My first thought is that it's about right. Everything costs these days.
On the other hand... semi - all accessible from a ladder - sounds like a day's work for a good handyman.
£20-25 per hour around here. More in cities like London.
It depends on what the downpipe re-aligning entails. "Running outlets" may have to be moved. That may mean new lengths of guttering (I'm assuming it's all plastic.)
Fixing downpipes doesn't take very long, but new pipe and fittings may be needed.
If all goes well, using a one-man-band or a handyman could shave £100 off that.
Since I'm sticking my neck out here, ask around and get another price. It would make me feel better. :o)