I've searched the subject and not found anything solid...if you'll excuse the pun

Anyway, from what I can gather, a pressured top hose with a bit of give is OK and the pressure should go when the engine has cooled down.

A solid top hose is bad.

Does anyone have anything to add to this?

Ta

No.

With the engine cold it's just water and you should be able to squeeze the hose.
With the engine hot it's water that's trying to boil but the pressure in the system is stopping it.
If the hose is rock solid when the engine is hot then there's extra pressure coming from somewhere else.
No it's not an exact science so if you're not sure either get someone else to squeeze your tube or compare it to another car.

The system is pressurised to 15 psi, each pound of pressure increases the boiling point of the coolant by 2 degrees F. Any pressure above 15 psi is vented from the cap. So you can see that with engine at normal temp the hose will be quite firm. If the hose ever goes solid it could just mean your cap is not venting properly. You can get the system static tested at a good garage, who can test for leaks at pressure, test the cap vent pressure and test for pressure build up as engine warms all with same test gear.