The pictures are out of focus, but from what you say, the likeliest explanation is aphid infestation. Treat for those and the ants will disappear.

Yes, I agree ...

Many thanks. So the ants are eating the aphids then.

I've just looked it up thinking that I'd have to get some special treatment but apparently if I spray the plant with dilute fairy up liquid it should do the trick. Hopefully in a week or two they'll be gone, fingers crossed ;)

The aphids secrete a sugary substance called Honeydew, and that's what the ants are after :)

Erm, not quite. The ants 'farm' aphids and scale insects for the honeydew they produce, so its what they produce they want, not the aphids themselves.

As for the fairy liquid treatment, I don't recommend it unless its with an eco washing up liquid, its no better for the plant and the environment than a decent insecticide, but its up to you. That sort of treatment only works on the ones currently present on the plant, and does not stop new ones arriving and setting up home ten minutes later. For a preventative effect, you need a systemic insecticide, which will keep working for up to a fortnight.

whoops, posted at the same time, Hywel...

:)

Thanks for all the further advice and the info on insecticides. Until I can get down to my local garden centre to get some insecticide I have seen another alternative remedy involving vegetable oil diluted with warm water. I might try this on a small section of the plant and see what happens

Update: I managed to get down to my local garden centre earlier to buy some insecticide, Bugclear. I sprayed a small section of the plant earlier, I'm sure it'll work in due course but it does seem to have the unfortunate consequence of killing the flower pod. It's a shame that the aphids are all on the flower pods and not on the leaves, still in due course I'm sure new flower pods will be produced and it's for the best. Thanks for all the advice thus far.

That's odd, these ready to spray treatments certainly don't usually kill flower buds.

Hi, thanks. Maybe I'm being a bit premature in saying that, perhaps those flowers were dying anyway. The whole plant has been sprayed now so hopefully in a few weeks there'll be flowers everywhere :)
There was never as many flowers on this plant as the other one. The aphids must be the explanation. I'm guessing they attack the plant and the plant goes into defence mode and stops producing flowers, or something like that.

It's more likely that one fuchsia prefers its environment compared to the other - you say you've one at the back and one at the front, so the conditions won't be the same. But aphid infestation certainly won't have helped...