Song from Theatre in Education

Okay I haven't got much information on this one, so it's a long shot. I recently watched a production of Thrills, Pills and Automobiles, put on by a theatre group at the school I work in. They used a song in the production and my attempts to identify it have so far been fruitless.

The song was sung by a female singer. It was a slow, melancholic number, and the only info I can remember is as follows.

The verse lines start with "What is ...." And contains the line "angels creeping" and references to sleeping.
The chorus has the line "only when I'm dreaming/sleeping"

I know it's quite vague and not a lot to go on, but if anyone recognises it, I would be hugely appreciative.

Try "Only When I Sleep" by The Corrs