We have to jiggle the handle to get it to flush. Cistern is filling up OK. What can we do ourselves or do we need to get a plumber in?

Please explain why you have to "jiggle" the handle? Do you mean you have to hold it down to flush or "jiggle" it to stop it freom overflushing? This sounds like a simple case of adjusting the flapper. With the flapper seated the linkage wants to have 1/4" of play. Too much play and the flapper doesn't get pulled back enough giving you a short flush. Too tight and it lets water seep past the flapper. I adjust the chain by the link and if it needs fine tuning, I bend the flush lever rod a bit untill I have the desired play in the linkage. One more thing about a flapper. you will see where the old flapper hooks onto the base of the white overflow tube. On a older type with no hooks the flapper has a ring that slips down over the overflow tube to the seat. If your tank has hooks, take a sharp knife or scissors and cut the neoprene ring off on the marks provided and hook the flapper on the hooks. Leaving the ring on will interfere with the flush. The water level in your tank should be 3/8 to 1/2" below the top of the overflow tube when the tank's filled. Good luck, Tom

Hi Tom, the problem is that the toilet is not flushing unless you really pull on the handle. I took the cistern lid off and pulled the lever inside and it still didn't flush so I think it must have something to do with the mechanics

OK! It sounds as if you might just have a stuck flush lever. Try to free it up with WD-40. If that don't work simply go to your hardware store and replace it. They're cheap and easy to replace if you remember one thing. The nut on the inside of the tank has a LEFT HAND THREAD. This means that clockwise will loosen it and not make it tighter. Good luck, Tom