Before I go in cack-handed any advice where to start…

Basically bike is in middle ring at the front and big ring on rear cassette.
I then seem to be have more push available on the shifter (as if I have another gear, which I don’t) so it jumps the chain off the top of the cassette. It won’t go into the smallest ring either – must be related?!

It’s likely that the drivetrain is worn but don’t think it’s at the end if its life just yet.
I’ve tried tightening the cable at the shifter end but doesn’t seem to making much difference.
Mech Hanger seems straight as far as I can tell.

Any pointers ?

Follow these instructions..

Firstly rear mech.

You need to adjust the limit screw on the rear mech so that it can never shift that far, whatever the cable does

then put the chain on the second smallest sprocket. With the shifter on the correct click adjust the cable so that the chain is just off climbing onto the next cog (3 rd largest)

you should be able to find youtube vids on both these procedures

front, no idea. May not be related

When I say smallest ring I mean on rear cassette. Sorry – should have been a bit clearer there. No issues at the front.
Thanks for replies

the chain jumping off the top of the cassette is the mech top limit screw, adjust that so the mech wont move further that the biggest ring ,
f you disconnect the cable it should drop onto the small ring on its own, if it doesn’t then the lower limit screw needs adjusting too, if it does then the cables too tight.
Have fun 😀

Cable’s too tight.