Hi Simon,
I do have a go on some things on the bike, I've replaced my rear brake pads, changed the oil and filter, balanced the carbs, but I don't have the greatest confidence and I need the bike every day to get to work so time is always against me, especially if I hit any problems or something I'm not sure about. I did think about having a go myself, I've got a friend who rides and looks after his own bikes who has said he will help, I may well do this.
The noise does stop when I pull in the clutch or roll off the power.
I know about the sprocket nut, I've read up about this and plan to get mine changed as matter of course anyway, I was planning on ordering the part this week :-)
Looks like it's bite the bullet time and pay out for a chain and sprocket, not sure what else it can be and it's certainly getting worse over the past 3 weeks from when I first noticed it.
Thanks for the advice :-)