Hello i have a bravo 1.8 HLX and for some time now been getting only cold air from the heater, initially i thought an airlock was the reason but after bleeding it numerous times it has not made a difference though have still not found the bleed screws The car does not overheat but does take a good 20 minutes to achieve operating temperature
if anybody could give me advise would be much appreciated

I'd start by looking towards the thermostat then check the heater flap is operating on the heater box.20mins seems long time to reach operating temp,20mins driving I take it?

Definitely sounds like a thermostat prob. It should hold the water in the block until it has warmed up which should take less than 10 mins really.