I don't know if its the best time to cut it back but it mite be worth it . also maybe dig over and rejuvenate the soil and give it a feed . it may well of come to its end .

Hmm, doesn't look good does it. It could be one or two serious things (honey fungus, phytopthera ramorum infection, fireblight) but its hard to be definite currently. I'd be inclined to cut the whole thing down, leaving just the stem, but you might want to inspect the base of the plant and all branches for signs of cankerous growths, oozing of any kind or soft, soggy areas, particularly at the base.

Often, prolific flowering is a sign that the plant has a problem, and all those flowers are its last ditch attempt to reproduce itself... but not always. Was there anything wrong with the Pyracantha you removed?

Thank you both for taking the time to comment on my question. Apologies for taking so long to respond. In answer to your question about the pyracantha, Bamboo, the only thing wrong with it was that my neighbours hated it as it was damaging their fence. To restore the peace, I removed it.

I think I may just have to bite the bullet and take the photinia out too. It may just have had enough after our very wet winter. I understand they don't like clay at the best of times and wet clay for a prolonged period may just have finished it off. I haven't found any growths or ooze.

It's a shame, as I rather liked it.
Thanks again.
Jane