With poor views and few details noted David, it is probably best to leave this one.
I can only offer guesses which we aren't be able to confirm one way or the other. Goshawk might be one such guess or just a Buzzard viewed in a strange light/angle.
Thanks. Henry.

**apologies in advance, no pictures and only a vague description!** On the train from Chester to Manchester, taking the route via Stockport, I spotted a medium-sized raptor perched on a fence. It was roughly Buzzard size and shape, but had a definite slate-grey back, dark head, and very pale breast. I know Common Buzzards can have a deal of variety, but I've never seen one with Peregrine-like grey on its back. It was fluffed up, which made it even more deceptive, and I was on a train so couldn't stop and get a really thorough look. So, I thought I'd post here in case anyone has any bright ideas, or knows of anything in the area that might fit.