Thanks for the input guys. The thing is when I emptied the first bucket in it immediately began to fill up as if there was already a blockage. Admittedly there was a fair amount of carpet fibre in the pan, undoubtedly! But this has never been a problem before so I am trying to figure out why this time so that it NEVER happens again!
The landlord is a distant relation. Not that that makes any difference. I have a feeling he didn't believe me when I told him I thought it was already blocked. Very difficult to prove of course as he was abroad while all this was going on! He is very well off with properties in Spain, Newcastle and lives in an affluent area of the town where I live.
Anyway ultimately I'm £60 lighter in the pocket as he had to get a drain block company out to unblock the toilet!!