I have the cam locking tool, pretty little blue one from draper CLT-K16
I will read up in my new Haynes manual on the job, but,
In principle it’s.
1. Line up all the timing marks to the correct posssitions.
2. Check with a mirror where the lower marks are,
3. Leave the car in gear and put the handbrake on
4. Insert the cam locking device but leave the belts tight
5. Put the rattle gun onto the offending sprocket nut and loosen only.
6. Check nothing has moved
7. Continue to take everything off ( bits of car, engine mount, belts, pump, tensioner and RHS sprocket
8. Carfully replace the seals without damaging anything
9. Put everthing back together following advice from this thread, other threads of more detail and the Haynes manual.
10. Turn the key and pray it works as advertised !
11. If YES then undertake a secondary FULL service and bring the car back into use.