Bob- if you heater hoses are not damaged then I'd be inclined to leave them alone. As for disconnecting the heater- I have yet to drive without the heater on, half the time I have the fan on as well. Perhaps this is a luxury of having a RHD car.
It won't be just a matter of replacing the hoses as the modern replacement has a bigger OD so you'll need new firewall grommets and a Dremel sanding-roll tool to open the ID of the grommets out by a few mm for the bigger hose.
Second issue is that the control valve on top of the heater is made of aluminum and performs a similar task to a sacrificial anode in the cooling system, being slowly eaten away from the inside by electrolysis over time. If the valve is original it is quite likely you'll snap the hose fitting/barb off in the process of removing the hose. No big deal as new valves are available, they are the same as used in Triumph Spitfire/herald etc. If you do replace the valve then make sure the new one comes with an oring as they are held onto the heater pipe by compressing an oring and the old one will be toast.
I read a great story about a guy that thought he'd quickly fix a leaking clutch master cylinder on a Triumph the weekend before a car show. Three years later he had a fully restored car.
Shipwrights' disease goes something like this:
Sailor owns boat.
Boat has burned out light in galley.
Sailor decides to change bulb.
Sailor notices socket is corroded, decides to change socket.
Sailor notices wiring frayed while trying to change socket.
Sailor decides to change wiring.
Sailor notices galley ceiling slats are rotted while changing the wire.
Sailor decides galley ceiling slats need changing.
Sailor notices ...
this goes on and on and on and on and pretty soon, Sailor is undertaking a
major renovation of his boat because of a burned out lightbulb.
Andy.