Thank you so much for your comments. Today, I have removed the head & found the head gasket to be in a pretty awful state so this is the number one suspect so far. Thankfully the head, combustion chambers & mating surfaces appear to be in very good condition with no signs of corrosion. Also, despite losing all coolant I can’t see any sign of damage to pistons or bores thankfully. One thing I immediately noticed is the look of the top surface of the pistons.One looking clean & bright with hardly any carbon or colour, whilst the other looks as I would expect after normal use & mileage (c.3,000 miles) ie light deposits, a little soot but good colour. I should mention that the clean side had a bore full of coolant when I removed the head. Is there any other area I should further investigate whilst it’s stripped down before re-assembling with a new head gasket? I still pondering why the radiator burst so heavily.