if something has fallen down from helicoiling then will still need head off won't i??? Yes. But if something from the spark plug, or swarf/piece of thread has entered the
cylinder then I would expect a badly scored cylinder bore as well.
That would mean a large garage bill to remove and strip engine to repair.
Would probably be better off fitting a known good second hand or reconditioned engine
when you start adding up labour and parts cost.
If your burning oil at a hefty rate, it's either bore/piston ring wear/damage, or worn
valve guides/seals. Both problems require cylinder head removal and the bore/piston
rings require engine out.
The garage will love you for the labour charges, that will probably be enough to send
them on a group holiday to Barbados.
The car will eventually fail an mot emissions test. If you really are burning a lot
of oil, and you've seen a car with warranty that you like, might be a good idea to
part ex it whilst you still can. Either that or budget for a replacement engine in your
Omega.
Either way, do what you actually want to do. I can't recall many folk on their
death beds saying, "I wish I'd bought a Nissan Micra".

Get and do what you want to whilst you can.