oooooooooh Mandym,
Im a very keen red robin fan and im always telling members just how good both a single bush or as a hedge the phontinia is and then i read this ref yours.

I have the red robin at the end of our swim/pool and i have another hedge of it on our drive and one more "smaller hedge in front of the greenhouse as they make first class protection from the wind's.

Now ive never in all the years ive grown phontinia had any problems at all, tonight ive checked to see id any thing is wrong and it isn't all those lovely leaves are now nice and red, very few have fallen off.
Perhaps give it one last chance and if this works out ok you've got your red robin back, if it shows no leaves then you'll be better off removing it "but you can say you tried".

You could try renovation pruning, have tried this with photinias with good effect, one of my clients is in the same situation as yourself, he has the varigated form, not been looking good he has used a fungicide on it, but last week we cut it right down and have watered it well due to the dry conditions, hope to see new buds break in about 4/5 weeks.

If you've got new growth showing at the tips, it isn't dead at all - do as Julien says, cut it back to a shape and size you like or want, give it a general purpose feed with something like Growmore (maybe under some mulch) water that in if you're in a dry part of the country (its like the sahara here at the moment, believe it or not) and it will shoot anew.

Thanks guys, I'm going to be brutal and give it a good 'pollarding' lol, that'll sort it out.