Thanks for the kind replies and Spiffingly Good, No, Zoe hasn't driven it yet as she has stopped taking driving lessons. She'll be welcome to use it once she has decided to start driving again.
Just the quickest of quick updates and a solution that may help others.
We're on the track of water getting in the car. The doors are being sorted (no inner plastic liners at the moment) and we have a very cunning plan for the door check strap opening (keep watching), but this one concerns the bulkhead plate.
I'd re-routed the heater pipes when I put the centre dash in and because I was using the older style heater tap & heated manifold, went to 1/2" heater hose.
The grommets I bought for the (Smiffy's) plate were too big for the pipe and too small for the hole in the plate. I cut & played around with them but despite the best efforts of some silicone, water still got in.
I couldn't find anything from the mini specialists so I started to look around to see what other grommet options were available and ended up on an electrical website. About this point, my neighbours nephew called round, (who just happens to be a spark), and 2 minutes later from the back of his white van........ a 25mm cable gland that was a perfect fit for the OD on the pipe.
A quick enlarging of the plate holes with a file, bit of washing up liquid on the pipe to aid fitting, and Robert's your Mothers Brother !!

And one final note.
I made it into print !!!!!!
Pictures from Bingley car park in Mini World and there I am, with Ratty the next picture along.
Best regards
Steve