The toilet up until 4 weeks ago had a very fierce strong flush. Then, it would not flush properly taking 2 or 3 attempts and that was just a pee and piece of tissue I now believe that where its not being flushed/pulled properly its backing up. I do not believe for one minute that a blockage in the sewer pipe which is what the Engineer has suggested, is the issue. It started with an issue operating the Toilet, and is not linked / anything to do with a sewer?????
If you're so sure, why are you asking here?
I'd check to see if your roof is leaking anywhere too, as this is also often caused by having a new boiler and central heating system fitted... Oh, and does your groceries bill seem higher recently as well?