Will I have to drain the coolant system to replace the 3 heater hoses at the rear of the engine bay coming from the fire wall (drivers side US spec). My concern is air getting into the system will I am replacing the hoses.

It will need to be drained to below the level of the lowest hose

How does lowering the coolant level under the lowest hose keeps the air out of the system. When the new hoses are installed they will have air in them. IF I fill the overfull tank and bleeding the system with the bleed screw, will that provide enough head to push the air out of the total system?

It doesn't, it will however stop coolant spilling all over the road/driveway/pavement/sidewalk (delete as necessary)

You will have to bleed the system once you have fitted the new hoses.
Usual procedure is to fit hoses and fill the system with coolant, (leave the cap off the expansion bottle for now) open the bleed screw and allow a constant flow before closing the bleed screw, (still keep the cap off the expansion bottle) set heater blower and temperature to maximum heat and run engine until it is up to temperature then open the bleed screw to expel any air and top up the expansion bottle, fit the cap, job done

Thanks 47p2!!! That's similar to what I was thinking.

Once up to temp rev the engine to around 2000rpm to allow the water pump to circulate the water round the engine

Got it. Thanks

you'll only dump about a quart replacing those 3 hoses.
trying to catch it is the impossible part.
siphon it out of the expansion tank, maybe?
i put a oil-change basin thing under mine, that got most of it. Jim
2000 NAS HSE
2005 NAS HSE

No harm in dumping the lot and refilling with fresh coolant