Howdy folks.

This is my 1st post so be nice

I have a 2000plate A3 1.8SE.
When it's cold it starts up fine and then runs fine, but when i've been driving for more than, say, 10 minutes, when i turn it off and come back to start it up while the engine is still warm, it takes a while for it to fire up then runs really badly. it also idles at 2500rpm. after a about 5/10minutes its then driving ok. The mpg isnt that great either. Is it just in need of spark plugs & leads etc or is something more sinister happening?

Thanks in advance for any help