What's this plant?

To me. it looks like a Fatshedera from the photo. It probably has been kept too dry and hot,and has red spider mite.You can wipe the leaves clean, then it needs spraying with a systemic insecticide. After you've got rid of the mites you should mist the leaves to increase humidity. Water it sparingly in the winter and keep it in a coolish temp. Good luck!

We think this looks more like a Schefflera Actinophylla (umbrella tree.)
Spritz is right about wiping and misting the leaves to increase humidity and he's also spot on with his suggestion to spray with systemic insecticide to get rid of the red spider mite. Scheffleras need strong but indirect light and should be watered only when the top inch of soil is dry. As it has no lower leaves, you may want to try something more drastic and prune it down. Hope you manage to breath new life into it!

Yes - sorry Elhenry, having rechecked book, I agree with LittleLarford.It's a Schefflera! Advice on care remains the same. Shame it's gone leggy. Hope the drastic treatment works!

You could try cutting it back as it is too leggy , and it will probably regrow.

Thankyou wonderful people.
I've now cleaned it and moved it away from the window. It's already looking great. I'm reluctant to use chemicals (my better half is a bit of an organic nut) so will it be ok to keep on wiping it instead?

Pest problems on indoor plants often increase rapidly due to the absence of 'good bugs' inside our homes as conditions are simply unsuitable for them to survive. Always treat all susceptible house plants at the same time. Trim, bag and remove heavily infested leaves and discard severely infested plants. Take the plants outside and spray with an organically acceptable oil or soap spray. Re-apply the treatment at one to two week intervals as long as the pest persists. If plants are able to be easily lifted, a regular rinsing under the shower, will help prevent mite problems occurring.

From the organic spider mite control website. Hope this helps