I finally got round to calling all of the UK dealers over the weekend, I got the following responses:
"No we don't do test rides on Dirt Bikes, they come back dirty".
"No we don't do test rides as we don't have an area to do them in".
"Sir, do you know thats an Enduro Bike"?
"No Sorry".
"Certainly Sir, if you come and see us on this date you can have a ride on an FE390 and an FX450".
I'll leave it to you to figure out who said yes.