overheating

[delbat]

no warm air from vents and thermostat rising on scenic when stationary

[qapmoc]

This might sound like a silly question, but are you sure that there is enough water in the system. This is exactly the behaviour you would get if the system is half empty of water !!

[qapmoc]

Or should that be half full ?

[Cockney_si]

Sounds like there is a blockage in the cooling system.
I had this on a Renault 21 way back.

You could spend hours removing top hoses and checking coolant flows around the system when the engine is finaly at warm-up temperature or you could take it to a garage and have them do it.