My wife has 1991 230e UK model 4 cylinder petrol. It has a hot start problem which is spoiling her enjoyment of the car a bit. The car takes a few turns of the starter if its been left for about 10 - 20 minutes. If its left to cool down it generally starts, albeit slowly, on the first turn of the ignition. It doesn't burst into life like my 1995 e220.

Our mechanic has fitted a new fuel pressure regulator but, if anything, this has made things slightly worse. It now takes a few seconds to start from cold.

I've read about this OVP but i've looked in the area behind the firewall behind the battery and all I see are two connectors attached to thick wired substantial wiring harness conectors and one small black plastic relay - no ovp with fuse on top.

maybe this car doesn't have one in which case I'd be obliged for any other ideas on the cause of this hot start problem.

Did you pull out the plastic shroud behind the battery? The relay is behind the plastic shroud. It is about 2-3 inches tall and about 1 inch square. It is usually grey or beige in color (colour). However I do not think this is your problem but check it anyway.

Yes, I removed the plastic shroud to reveal the plugs i refer to. No sign of an ovp though.