With a budget of £500, I might suggest you don't look for vintage Omega, because anything worth a darn will be three to four times that amount.
I do get the desire, for sure! I have some nice vintage Omega in my accumulation, but anything you can get for that price, you don't want.
You might look at vintage Tissot or Lemania, those were in the same family of the time. Perhaps even look for vintage British-made watches.
I do not intend to dissuade you from this quest, but a vintage watch you intend to wear is not only the purchase price but also a commitment to a lifetime (not yours, the watch) of maintenance. Vintage Omega, epecially early automatics, are frequently worn out in expensive places.
Perhaps look at models with an 1120 movement. Those are new enough to be easily repairable, and there are some nice models.
Or ask for suggestions.
Again, I do not want to dissuade you, only mention that any model similar to those shown in your pictures are beyond your budget, once you include restoration.