[robchalmers]

My recolection is that it took my dti roughly 8mins (5 on Mway) before the car had reached cruise temp - I too noted the effect of switching the heater on had on engine temp- its like a second radiator I used it in heavy M6 traffic to kepp temps down. simply put heater and blower on full and open only the passenger face vent and blow it out the passenger window!

if you want to bring the temps up quicker try altering the water/anti-freeze mix