Well I got bored after work today and set the heater to fire up whenever i want it to, from cold it took just under 5 minutes to warm the engine up and cut out while the engine idled. I'm going to take the car out later and time how long it takes to warm the engine while the engine is under load. I also found out the heater will carry on heating even if i turn the engine off so i would still be able to EOC while its warming the engine, or even let it warm the engine before i set off
Andy