Got this really annoying problem

When the car is cold it will start first time, but when it is warm it really struggles to start.
It will normally go second or third time if it will go at all.
I have had the car set up, but no difference.
Its pretty much standard other than a chip.
Tried changing plugs etc but made no difference.
Also if you leave it ticking over for a while it fouls the plugs up and when turned off it wont start at all.

Any help would be apreciated.

Oh and the car is a 88 Escort RS Turbo if that makes any difference.