You have a cushion scale infestation - the white masses are where the eggs are/were, the sooty mould is in association with this infestation. Check the backs of the leaves, you might be able to see hatched scales - they look like yellow things, usually found either side of the central rib on the back.

Spray with Provado Ultimate Bug killer or Westland Resolva Bugkiller/Bayer Sprayday greenfly killer, being sure to spray both sides of the leaves to run off. The last two are contact insecticides, the provado is systemic, but the provado contains thiaproclid, which is bad for bees. Spray when bees are not working, around dusk, whichever spray you're using.

Thank you Bamboo for replying so quickly. I've already put provado on so hopefully that will start working soon. Can't believe how bad it is. Poor thing hope it perks up soon.

Provado make more than one treatment spray - the Ultimate Bugkiller one is the right one to use on this.

Thanks that's the one I have used.