So crunch time now, bargain banger or something newer. Hummmm
I would seriously look at repair costs if you think it is the HG, as a banger will need £500 dropped on it to fix its niggles, plus the unknown element, and what you've been looking at will need constant work - the nature of big bangers. Given your current status, you could do without that. At least your car is a known entity, and a trusted garage would not be all that dear, as discussed privately.
The Omega Elite is a very hard car to match. Irrespective of price.
Or bite the bullet for a near new car, if you can afford it, if just for commuting, a small far east shitbox costs next to nothing at about 3-4yrs old.