Have you tried pouring bleach down it and leaving it for several hours?
thanks Dave for your advice. I called a plumber and he cleared the blocked the toilet in thirteen minutes. The 365/24 hour coverage from Homeserve was only the time they answered the phone.
Homeserve said they would respond in five days to clear the fault. They made me believe they were a 24 hour 365 service which was false.
Now they constantly send letters to rejoin the programe.
I paid £50 to clear the blockage by an independent plumber, but had already paid Homeserve ever £100
I would advise not to sign up to Homeserve