Update,
Coming up to Christmas, €400 is a bit of a dent in the finances. So...

I’ve discovered that Corteco is/was the OE supplier to BMW. I then compared online pics of Corteco TVDs to the original one from the car dated 2007.
They are identical, even down to the same casting marks and codes on the rear.

I’ve ordered a kit including new bolt. Guys on rover forums swear by them on the M47R engines they use... reports of several years without issue.

John