spray with a mild soap solution will work if you are after an organic remedy. if you dont mind the chemical alternative there are many insecticides for sale in the garden centre.
welcome to GoY too.

Thank You for your comment. It's very useful. :) x

spray with mild soap solution

Note that the soap solution will only kill the aphids it touches, and getting the ones deep in the rosette will be difficult. If the soap doesn't do it, look for a systemic insecticide, such as Provado or acephate, as a back up.

Whatever you do, do not spray with any commercially available insecticide, all Crassulacaea turn black and die when sprayed. Don't ask me why, but they do. Not even sure that soap is a good idea either. Before spraying with anything try to wash off the critters with plain water and a strong (ish) jet of water.

If there's not too many and you are not squeamish....just squish em!!

Thank you peeps, I will use plain water first and will let you know how I get on. :) xxx

That's strange, Owdboggy! I've never had any problem. But I've found that you definitely don't want to use any aerosol spray: they are all oil or alcohol based, and are death on any plant with a significant wax coat on the leaves. Products in pump spray bottles should be labeled "water based" and "for houseplants".

I haven't been on here for ages, (mainly because i forgot my password) but i did manage to get rid of the greenfly with a mild soap solution and my plant is doing really well. thanks for all your advice!!! its been much appreciated :)

Excellent!