Since having a new head gasket i've encountered a few problems with my rover 45. Firstly the oil had mixed with the water and had gone everywhere possible prior to the new one being fitted. Now the car runs rough on tickover and the tappets are noisy. The pipes to the radiator go hard once the car gets up to running temperature and their's only cold air blowing out the heaters. The oil and filter has been changed with engine flush added to old oil. Also rad flush has been added to coolant. Can anybody help please?

Noisy tappets can be due to the oil contamination. They may get better with the flushing oil and a bit of running, otherwise they will need cleaning or replacing.

Heater performance - assuming that the engine does not boil up, this will be due to mayo blocking the matrix or valve. Try flushing it and then running with some system degreaser in it (not cleaner/descaler). If the engine boils up, then the heater problem will be due to an air lock.

Make sure you bleed the system properly (From MG Rover tech bulletin)

Remove bleed screw from coolant rail
Fill expansion tank to just below neck of tank
Insert bleed screw when clear coolant comes out
top up tank to below neck
run engine with coolant cap off at 2500 rpm until expansion forces coolant toward top of tank
Replace cap, run at 2500 until fan cuts in, run at idle till it stops

Surely hoses should be relatively hard, the overpressure prevents the coolant from boiling?