If your privet hedge has been there for a while it has probably drained all the nutriment from the soil, they are gross feeders. Get a load of well rotted manure or compost and fork lightly into the soil along the line of the hedge. We got rid of one that was a good metre wide and replaced with a fence but had to put a lot of organic matter into the ground where it had been.

Was going to say the same as Moon_growe: feed the roots with well rotted manure. I was wondering if it is worth a foliar feed as well? Also is it near a road? Councils have changed the salt they use (you should have noticed that it is no longer orange brown but now white) and the white salt seems to burn hedging a lot more.

You might also rejuvenate the privet with a really hard prune. I wouldn't normally be in favour of saving privet but you have a use for yours.
Do you cut the tropaeolum back at all? You could do the two together - cut my privet back at this time last year and it has come back (not that I particularly wanted it to but it's only waiting until I can find a blacksmith who will make my iron railings and then it will be out!)

Yes agree with the above, privet can be easily be rejuvenated, then it's a case of trimming it regularly to keep it compact, the trapoleum will keep coming up,just be careful where they are when you are rejuvenating it.

Balanced feed would be good too especially after a hard prune, then a foliar feed may/june time, no later may help......

Thanks for your help everyone. It's now had a couple of bags of manure forked into the soil. What a lovely way to spend mother's day :)
MG - thanks for taking the time to answer. I think it has been there for years. Hopefully the manure will do the trick.
Botanic - it would be a real treat if the council salted the roads and pavements round here! But know what you mean about changing the salt - I've noticed it elsewhere. Which foliar feed wouldl you recommend?
Urbanite - I'm not a particular fan either but the fact that it serves a purpose is the only reason it stays! The Tropaeolum dies back each winter and rejuvenates each spring so if I need to cut it back next year, it won't be a problem if I do it early enough.
Julien, thanks - as I said to urbanite, if I do it at the right time, the Tropaeolum should be find.
Pam - thank you for your comments. Would you recommend a particular foliar feed - there are so many out there, I get confused!