I'm going to call you out on the tenants remaining in the property for "several years". That simply wouldn't happen unless you didn't follow the procedure to evict them.
UK laws are very much in the favour of the landlord.
UK laws are very much in the favour of the landlord.
But without going into detail, I definitely buried my head in the sand too much, and they did pay a small amount at one stage to make me think it might be okay. It was sixteen years ago now, and I've thankfully forgotten a lot of it.
I do remember that I had to restart the whole process when it was thrown out because a date was wrong on a letter. I wasted a whole heap of time trying to get the judge to reverse that decision rather than moving on and starting again.
Anyway, like I said, I was very naive back then, and made lots of mistakes.
Sorry you've had such crap tenants. 16 Years is a long time, and the laws could have changed on this in this time. So there is a good chance you are both right!