Personally, I wouldn't consider throwing the money required to do these repairs and a decent paint job on a 2.2 Omega. Once you have to seriously start chasing rust....
I appreciate all models are becoming thinner on the ground, but I would be tempted to bide your time for a suitable replacement to come up. V6 models are far more desirable in my opinion, and although you may have a sentimental attachment to your 2.2, the sentiments will soon move to any replacement. There is however a much greater chance of finding a decent 2.2 than a V6.
There are some than may state you must factor in the cost of a whole front suspension rebuild for £1000
, but this is just a 'across the board' statement. You'll know when the right car crops up - a genuine, well maintained original car is a far better prospect than a 'so called' repaired / restored car, and will retain its value better.
But it depends again on how long you are prepared to wait for the right car, how much you are attached to your current car relative to how much money you want to throw at it.
The majority of these observations come from years of owning classic Triumphs, and pondering the exact same questions for years that you have asked - and I have not regretted my decisions in waiting for / finding genuine original cars.