You have a rental property with ptsb. Was this originally your home? If so, you might qualify for a tracker mover product. I have summarised the conditions
here.
If you get a tracker mover, this is by far the best solution for you. You will pay an extra 1%, but that is much better than paying a high SVR.
1) You will need to sell your own house first.
2) You will need 10% of the cost of the new house
3) You will need to meet the income conditions - but this seem the least of your problems.
You have not told us about what deposit you have, what other assets you have or how much you want to pay for the new house.
But assuming you do not have buckets of cash, you are only just out of negative equity, so you should not buy a second house as you would be too exposed to property and borrowing. You should sell your own house first.
If you can't sell your own house in time to buy the other house, have you any wealthy family members or friends who could buy the other house and sell it to you when you are ready to buy? This is an option these days as stamp duty is only 1%. If it's an absolutely unique opportunity, it's worth considering.
Brendan