ACE 2.0 16V Hot Start Problem... CTS?

[Ringmaster]

Still having a mare with this engine. Replaced a few bits and it is better but this hot start problem remains.*

If I drive the car for a short distance, say 10 mins, shut off, then start it again within 5/10 mins it seems fine.*

However, if it's had a good 30 mins plus running, shut off, then start it again about 20/30 mins later it just won't idle. It turns and fires ok, but unless I give it a bit of throttle it just dies. Tried holding the revs for a good 10 secs but as soon as I take my foot off the throttle it dies.*

It seems there's some relevance to the engine being shut off as I can drive for as long as I want once it's warmed up and it doesn't stall. It's just once I park up for a bit and get back in that the problem arises.*

So does this sound like a dodgy coolant sensor, the one near the dizzy? Or something else?

[Ringmaster]

PS, ignore the asterisks, posting on android is a right pain...!

[Monkeymagic]

Injector seals hardened? Is it giving any codes?

[Ringmaster]

Was giving throttle sensor and lambda codes last time I got it read. Replaced lambda with proper bosch - sorted the hesitation etc. Throttle sensor - mech said the one on the tb looked almost new but a bit out of adjustment on the two screws. Readjusted and with lambda drives well.

Not had a chance to get any more codes in the last couple of weeks. Briefly gives the (!) and coolant warning on startup, oil light also intermittently but that clears after ten mins or so.

[Ringmaster]

Forgot to add, coolant gauge hardly gets above 70.