Let's assume you can get a mortgage. Your position after the mortgage will be
|total|self (1/12)|wife|New house|cash
Value| 840|150|190|450|50
Loans|850|200|200|450
You have €180k of gross income a year
Current excess of repayments over rent: €10,000 a year
It seems to me that you would have excessive exposure to property at over 4 times your income.
You would also be very vulnerable to the eventual interest rate increases.
Not possible to sell (jointly held property) at the moment so viewing it as owning it for the long haul.
Why is it not possible to sell this? It would make eminent sense to sell it. You don't give the rental income, but as it's a variable rate mortgage, it's probably not making any money for you.
Your wife's house is probably very profitable in that the rent probably comfortably exceeds the interest payments.
But if you are with one of the main lenders, you should be able to sell this and transfer the mortgage to a new house. This is what you should do if allowed.
If you are not allowed to transfer the cheap tracker, then you should continue to rent. With property worth €340k already, you will have good exposure to the property market. So if property prices rise, you will benefit from the rise.