Strange first gear noise

Hi all

Just picked up my first vrs, a 53 plate black one, it's done 153k miles and from what I can see is fairly standard.

The only issue I can see at the minute is when I pull away in first I get a strange sound, a bit like running on 3 cylinders, but doesn't do it in other gears and isn't related to speed.

Any ideas? I will try to record the sound it's making. I'm hoping to get a good look over it at the weekend.