Thanks Bob, I did get all that interior trim off last weekend and located a nut but could not shift it with the leverage I had in there and didn't want to force it too much. I also saw that there was a bolt with what looked like a torx head on it it that had been completely mashed up by someone so I had no chance of loosening that either. As I wasn't sure which one I needed to remove I decided to leave it for another day.
If you are certain is the hex nut rather than the torx bolt then I will summon up the energy to have another go!
To make myself feel better about my failure, I replaced the pollen filter and gave the car a bath instead 😀. Only washed it, I will get out the rotary polisher another day too. Here are a couple of pics, Roy