Thanks for the responses everyone....

This is why I am hopeful it is a simple case of a clip allowing a hose to lose coolant as opposed to a head gasket - although I admit the worst cast scenario is still possible of course.

The car drives perfectly, no problem with performance, no smoke, no nothing that would tell you there was a problem with anything really. The car, despite its age and mileage (just done 90k with a new timing belt and water pump fitted by the garage) is spotless, and drove far better than 3 other cloverleafs of similar age and mileage that I test drove.Not even a single noise, rattle or squeak from anywhere when it is driving.

I have found a thread from 2012 on an Alfa owners site that stated some did have issues with a hose clip struggling when the coolant system was pressurized due to the clip type - so I am really hoping it is just this.

I am contacting the garage tomorrow to discuss what I can do. It came with a warranty yet I cannot imagine this would be covered as surely a head gasket fault could be down to the previous owners lack of maintenance (if indeed it is a head gasket issue). Whilst if it is just an issue with a hose or clip, then hopefully they will just sort it.

I do hope it is just a lose or misfitting hose that is the issue.

Firstly air cannot just get into the cooling system and get stuck. That's a total myth. Second the absence of milky deposits does not necessarily mean the head gasket hasn't failed. The gasket can fail in several ways. Oil and coolant will only mix if it has failed across those two points. The cooling system will be compressed if the gasket has gone between a cylinder and cooling jacket. If this is the case then exhaust gasses will be present in the cooling system which would be detected by a sniff test, especially on a petrol engine which gives off carbon monoxide to which the detecting liquid is sensitive. Check the temperature of the radiator when the engine is hot. It should also be hot, but will be slightly cooler at the bottom than at the top. If the engine is hot but the radiator is cold you have a clear problem. The job of the radiator is to dissipate engine heat. A radiator is the wrong name for it because it doesn't radiate anything. It's a heat exchanger that conducts and then convects heat. Engine heat will not be dissipating if the radiator is cold. It does sound like you have a cylinder head gasket problem, but anyone with a good working knowledge and a pressure tester, as well as a sniff tester should be able to confirm or dismiss it.

Firstly air cannot just get into the cooling system and get stuck. That's a total myth.

Yes it can.

So no, it isn't.

Absolute rubbish, no it can't. Air and coolant cannot occupy the same space, and air cannot enter a sealed system and force coolant out of the way. Where do you suspect the coolant will go once this air gets in, and how could it get in? The only way air could get in is if the system is breached, such as via a blown head gasket or the system having been drained. There would be overheated cars broken down everywhere with air in the cooling system if this was the case.

In a sealed correctly operating cooling system air cannot enter, simple as that

See above, particularly the "after a drain and refill" bit.

This none-too-subtly implies that, in the example experience I'm relating, the system suffered a persistent airlock "after a drain and refill".

I know this because I drained and refilled it

That's why I said "after a drain and refill"

This may not apply to the OP's Alfa, but AFAICT we don't know it doesn't. As I understand it, he hasn't had it very long, and does not know in detail how it has been maintained.