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The original problem (how it got blocked), I'm told, is the original bathroom fitter has put the shower waste pipe too far into the main waste pipe and the toilet waste pipe falls in above the shower waster pipe, so loo roll and stuff that goes from the toilet has not all been going down the main waste pipe but sitting ontop of the shower waste pipe (that is just below it and jutting into the main waste pipe) - eventually the build up caused the problem I encountered the other day.
The other problem was that the waste pipe from the toilet has two flexi bends in it and you are only supposed to put one in so debris has been building up in the second flexi bend as well. This is all the "work" of the original plumber.
The emergency guys who came to fix it took the waste pipe off the toilet to clear the blockage and said that the waste pipe wasn't fitted properly - it literally fell of the toilet in their hands - so yeah the leak is probably down to them not pushing it back on properly and I am going to get them to come and look at it again.
What I am worried about is the WHOLE problem having to wait until September 11th to be able to get the original fitter back in and hence my question about where I stand if I get someone to sort it PROPERLY and PERMANENTLY and then invoice the original bathroom fitter