I had water coming out of my toilet overflow. The plumber I hired changed the washer at my suggestion. However the toilet then made a noise when flushed so he took out the old style plastic float ball valve and installed a fluid master. This caused banging in the pipes (reduced the flow with the stop cock to reduce this) and after he'd left there was a leak from the toilet cistern! This didn't fill me with confidence so I hired another plumber.The second plumber installed a Torbeck valve but without the high pressure flow restrictor. I still need the flow turned down too low otherwise at the end of the flush cycle not only do I get water hammer it also leaks slightly from the stop cock. Even with the flow restricted I still have to hold the arm of the Torbeck valve down at the end of the flush cycle to prevent water hammer. HELP !!!

1)I suspect that the water pressure maybe high (but I'm not sure). Do I need to find out if this is the case before hiring a fresh plumber so I can advise him about this so he can put the right valve in the cistern. If I need to find out if the water is high pressure how do I do this?
2)What valve do I need ? Should I insist on the old plastic ball style valve ? Or can anyone advise on exactly what type of valve I need ? In fact should I buy the valve before getting the plumber to ensure the right one gets fitted ?
3)How do I find a reliable good plumber the first was recommended by a local plumbers' merchants. The second was registered with the Institue of plumbers.
Any Advice gratefully received.

Thanks