Any car mechanics here?

Over filling wit oil is UNLIKELY to cause too much damage. I massively over filled my Astra once and all that happened was plooms of smoke when I tried to give it any revs. Thought I'd blown something but it was just the pressure pushing past the piston rings.

It's more likely that the rad has caused the damage.

[BanannaMan]

It is possible for a blown head gasket to cause a radiator to fail although they usually split along the seam or look puffed out near the leak from the high internal pressure. (Usually results in a split though and not just a hole.) Air or exhaust can enter the cooling system near the valves through the blown head gasket and cause too much pressure.
Does the radiator look like it exploded from the inside out???
If not..It's likely the hole in the radiator caused the motor to overheat...doing in the headgasket.

As mentioned earlier...the elevated oil level may be from coolant in the oil.
However it is not likely (though not impossible) that you would have both too much pressure in the system and coolant in the oil.
If so your head gasket is leaking in more than one place and you'd better have the head checked for cracks. (not a bad idea in any case)

The oil is not the cause.
If there is too much oil it can cause oil seals to leak but would have had no effect on the headgasket.
Check to see if the oil is "milky" looking or if any coolant runs out of the sump when the drain plug is removed.
If you're not doing the work yourself don't bother draining the oil.
It will have to be changed anyway as a small amount of coolant will enter the motor (via the cyls.) while removing the head.

Don't drive this car anymore or run the motor other than a few seconds for testing or you'll likely be needing the entire motor replaced.

Cheers all, decided it's an uneconomical repair.. Scrap value only now.

Thanks for all the replies.

What Bannaman said

I had a car (Hillman Imp for those old enough to remember ) that blew 2 radiator hoses on the same trip due to a head gasket going.

Therfore its reasonable to assume that if the weakest part of the cooling system is a dead or dying radiator then the pressure could blow that if the system has been presurised by the cylinders