Am I right in remembering my old 16vt only had one bonnet strut which you had to 'break' in order to release? My 20VIS has two conventional struts is this normal or a mod?

Yes my 16vt had a break-point half-way up the n/s strut with a red cap, which the ignoranti used to regularly break by forcing the bonnet down before releasing it.

Most later models have two identical struts which hold the bonnet up and can be depressed equally when closing without any such procedure.

Thanks, reassuring I'm not completely senile then! (yet)

Different slant on this, I've often wondered if anyone would have come up with a hinge bracket for the bonnet on the the likes of older cars. Just a thought.