[jor]

There is a write up by tfb on how to do it. Might work out to be more expensive than a garage as tools are needed; at the least a 450Nm wrench, tool 5192 which stops the idler rotating when undoing the bolt plus the timing gauge and adapter to reset the timing. It's not something I would have contemplated doing without having seen someone do it first. Might be worth asking John Davies if he could be of assistance.

jor