Rover 25 power loss problem?

I have a 2000 Rover 25 1.4, which starts from cold fine and runs really well, but if I start it from warm ie if I've been to the supermarket for 10-15 minutes, it starts ok but loses power on acceleration and jerks and splutters then all of a sudden goes like the preverbial off a shovel nearly breaks my nose on the windscreen and is then fine.
Any ideas welcome

Michlou
July 2008