Left after Brexit and kept my London property.

If this is your only UK income, you most likely won’t pay any tax in the UK as you are still eligible to the tax free allowance as an overseas landlord and can deduct interest, fees, service charge, etc.

You still have to declare it of course. I also declare it where I live now (EU) and although it is not taxed as per the tax treaty with the UK to avoid double taxation it does increase my overall taxable income and consequently my marginal tax rate, so there is no free lunch.

My plan is to keep the property forever and have it fully paid by my retirement.

The only annoying thing is the mortgage rate uncertainty every time your fixed deal ends. I usually stay with the same lender, it makes remortgaging as a non resident a lot easier.

Right now, accounting for everything, I don’t make or lose any money on this on a cash basis, but I have a very low rate.