The chain is rubbing against the front mech when I'm on the smaller cogs at the back – doesn't matter which ring I'm in on the front.

What's wrong? Cable too tight?

I haven't changed anything on the bike recently but I think it's a new problem.

Is it the inner or outer part of the mech that the chain is rubbing on?

the outer side of the chain is rubbing against the inner side of the mech.

you need more cable tension, to move the mech further away from the frame. Happens when cables stretch.

cheers reggie – I'll give it a go

It may be worth putting the shifter in position 1 (granny) and checking the cable tension first, as you may need to pull more cable through the clamp on the mech rather than adjusting the barrel adjuster.

Ta. and if I need to tighten the cable at the barrel adjuster it's ANTI-clockwise right?

Thats correct.

Also check the max movement by your front mech (over ride)

It could be restricted by the screw to stop it going too far but only check if the cable is already tight as stated above^^^

Front mech into small ring
Screw barrel adjuster all the way in then out 1.5 turns
Undo cable at mech
Check mech is sitting in correct position on stop screw – adjust if necessary
Pull cable just tight, then tighten it back up
Test and adjust at barrel if necessary

If it's suddenly started, i'd check that your mech is straight first, a good clout can sometimes twist them.