After searching loads of threads on here I'm none the wiser as to why I'm getting this noise.

There's a nocking sound coming from the engine, I say nocking it sounds more like a drumming noise, it sounds like a plastic box being hit or tapped. Its a dull deep noise, Its not loud but it is noticiable while driving. Its also present faintly when in park but it gets gradually louder with revs.

It wasn't doing this until last week. I can't get it to my mechanic until end of next week.

Any ideas what it might be.?

It sounds like its coming from the left side if you are looking in to the engine bay.