"Longer term the house would be if I found the right girl, marriage, kids, etc as she would be wanting some reassurance that I would be staying around and somewhere for the kids, etc."
How do you propose to pay for day to day living, because £450 a month rental income won't cut it? Run down whatever savings you have left after buying a house? Kids cost you an absolute fortune. Remember all the posts where you say Ukrainians don't earn much money? That would be the job market you would be trying to enter. Even working in a Irish pub they would need you to know some Russian.
I've got a few ideas for extra money not saying they would work out, they might or might not. Well, if difficult to work out expenses from afar. Ukraine is a different country to the UK so costs are different. I know Ukrainian women in retail jobs earn about £100-150 on average, maybe a man would earn two to three times that. So for a couple I don't think the £450 would be too bad to live on. For a family, well it is probably more than doable but things might be a bit everyday living. So it then comes down to any extra I can earn at whatever and any extra she can bring in or any money from the government. Over time money from the rental would increase and mortgage repayments most likely decrease in real terms. So the outlook I think would be pretty decent. I definitely think it's worth a go. Plans of course can change along the way but to my mind it's got enough go in it.
With £450 a month that's an easy £100 a week for food so that's enough for the UK in Ukraine food prices are likely cheaper outside the city centres. So in Ukraine it should be more than doable. End of the day with two people at a bit of a loose end one off then should be able to sort something out for a bit of extra income. Remember this won't likely happen overnight so plenty of time to work things through should it this all come about.