You can get a little more value out of that property if you claim depreciation. (Assuming you’re not already).
For the building itself, you can claim 2.5% of it’s value until the building is 40 years old. There is a slightly different rate if that property was built between ’85 and ’87 but thats a long story.
How did you come across the block of flats? Were they on the website you mentioned (Which property type would they come under?), or did you find them through an agent?