Hi again , just an update , I took my bike to a bike shop after finally giving up on it , I had the gears tuned etc after snapping the first chain and fitting a second , all was fine until the first few miles then it started jumping again , after close inspection I realised the links were getting tight , not good on a brand new chain ! I looked at the writing and instead of saying narrow it said ‘marrow’ I googled this and apparently there are fake chains about ! Just letting people know !