Cherry tree not well

Looks to me as though your blossom has been a victim to the frost.  You may not get as many cherries as expected this year, but apart from that I can't see anything else wrong with the tree.

I can't quite tell from your photos, but do the leaves on the dying back branches have a slightly silvery sheen to them?

Silverleaf is a fungal disease that usually (but not always) gives this appearance, and makes whole branches die back.

Another way to see is to cut a thickish branch off (about 2cm or more) and see if there is a brownish stain inside.

I can't think of anything else it could be but will check the RHS website and get back to you

OK here is wht the RHS say, and it includes a photo but there is also a comment that there is something called false silver leaf, not bacteria, which does not have the brown stain inside the wood, that is caused through stressful conditions........

Hope that helps
 http://apps.rhs.org.uk/advicesearch/profile.aspx?PID=245