Hi Vince and another
To flush or not to flush: that is the question (with apologies to Bill Shakespeare's Hamlet)
I'm on the fence with this one and I'll admit that I probably wouldn't bother unless the coolant looked very dirty. I suppose it depends how the car has been stored.
If it's been parked up and left sealed up with antifreeze/inhibitor in the system then I don't think you'll have that much corrosion in the main tubes and engine block. There will be some of course, but you need oxygen for corrosion and from the header tank downwards, with no circulation, the access for oxygen is restricted. The inhibitor will degrade over time so you could expect something but probably not tragic.
If it's been left drained and open then I'd fill it up with water, run it for a few minutes then drain & fill with antifreeze/inhibitor.
However, if it's been stored with the system partially drained and open or with plain water in then all bets are off and I think I'd strip/clean completely.
There's certainly nothing wrong with uncoupling the radiator hoses and draining/flushing as best you can to clear the main tubes. If you're going that far then I'd also uncouple the header tank and drain/flush that separately because that's the obvious place in the system for an air/water interface and usually where you get most corrosion. It would be a pain if you flushed the radiator, started up and then filled it up with rust from the header tank !
Personally I'd start it up, check for leaks at the water pump and then drain the system from the header tank first and then the radiator/block/etc. Depending on what came out I might even run a system flush before draining and re-filling with fresh anti-freeze/inhibitor.
As John says, internal corrosion with an iron block/aluminium head is a problem you don't want surprising you down the line.
Brian