When I moved into my house five years ago I took out British Gas Homecare 400 which covers my gas, electricity and water. I am so glad that I did as I have called them out several times with plumbing problems, leaking radiators, faulty electrical sockets and a temperamental boiler! After having a new boiler fitted last year, I now pay less than £30 a month.
My most recent problem was with my toilet which began to gurgle after the flush and the water level in the bowl was very low. After a quick phone call, a Dynarod plumber came round and identified a partially blocked drain which like the OPs toilet problem, needed a different branch of Dynarod to fix. But they came out as an emergency as it is my only toilet and took up manholes etc, flushed through and off he toddled. A couple of days later, the same thing happened again and when I called BG Homecare, I was treated as a priority as it was an ongoing problem and this time the correct action was taken to remove a blockage which was in my waste pipe before the manhole ie my responsibility.
My point is that I did not have to find a plumber and be faced with a extortionate bill, all these call outs were covered by my annual contract. Yes, I know that if I had not needed to call them out, I would still have paid each month but for peace of mine I think it is well worth it. I reckon I am well in credit based on the number of times I have called them! Certainly worth it is you do not have a local plumber, electrician or heating engineer to rely on.