Got there in the end, you have to press the buttons in a different order to what is stated in that post.
If anyone's interested, my car is a 2015, serviced every year at a Honda main dealer by the previous owner and the Connect unit has never been updated.
Luckily I've managed to get it booked in at a dealer who offered to do the RC8 update for a very sensible price, just got to wait 2 weeks and hope it doesn't get bricked. Thanks for the info.
Now I need to find a replacement phone with MirrorLink, any suggestions on an Android phone that works with RC8 appreciated, especially if it can display Android Auto on the car screen
Why not update to RC8 yourself?
It is really very simple, 3x USB sticks and inserted into the USB port in the car in the correct order with the right file written to it that suits your headunit in the root of each memory card. It'll be a lot cheaper buying 3x USB sticks than the garage price and while worrying, is a complete non-event. I did mine twice now and did not have a problem, I kept the car running so as to avoid the radio going off while doing it. I've also rooted mine to allow me to install apps again now it's running RC8.
I am curious how much they are charging to do it though?
I am using a Samsung Note 9 and that works via Mirrorlink all ok, it's not the best system compared to Android Auto and is a little clunky, but it now works.
On the subject of Android Auto you will never have it sadly, unless you buy a 10G which comes standard with it. All 9G's will never recevie it as an update.
The other option is to replace the head unit with a 3rd party Android unit which does have Android Auto and Apple Car Play, which is a viable option if you're ok going that far.