Just to add to this I used Shaikley Motor Company in Colchester to do my timing chain tensioners, was a success but cost over £4000. Makes such a difference when it’s done. There’s a special locking tool you have to buy apparently which was some £300/400. They now have the tool (which I paid for) so perhaps other owners can benefit.
Used Dartford transmissions (mentioned above) for a service/find a vibration recently, very not recommended.