HI thanks for that and I have gone a bit further, I set the tail to center and servo to 90 and that has got rid of the buzz, TX trim to center, on lift off I have to hold quite a bit of right to stop chopper from turning. I had struck the tail rotor the other day on a plastic bin
and had to replace the gear set part 26 as it stripped. Have I done something to rotor assemblely? it all looks fairly straight?

Second problem on lift off looking from the back of the chopper I have to trim aileron to the right to stop drift (swash plate down on the right hand side) so swash plate was nice and level but now have to trim to the right to hold steady how do I fix this?

Thank you for your help