The warning light kept coming on after a service - took car back to garage where they said the reluctor rod has moved one tooth and car needs a new engine - can anyone give me more info on this please?
Pulling together a lot of good info from the comments:
Pretty sure a "reluctor rod" isn't a thing per se. Reluctor wheel is, so I'd assume this is what they are talking about. Maybe even chalk it up to the Aussie name for the part.
Replacing the entire engine seems like an aweful lot of a stretch. If the timing was off by 1 tooth, its doubtful you'd need a whole new engine. Depending on the exact design of the engine, that might not even be enough for the piston to contact the valves (which is presumably the damage they are worried about).
If you have a borescope, you could look in the sparkplug holes, find a cylinder where the valves are pushed down, and examine to see if they are damaged.
Or you could turn the engine over yourself with a wrench on the crankshaft. If it gets stuck, then I'd worry that something is damaged. Might want to take the sparkplugs out for that too to make it easier to turn over.
EDIT: and get the codes that it is throwing, this can provide additional insight