I like you Chris, so I'm not going to do my usual thing of asking to borrow your wife or drive your car (long story).
With the amount of experience you have, you'd be better to ask if there's anyone in the area you can be a Go-For for, in exchange for a little field training. That'd probably be a better route to go down.
Find a local shooting club and ask the guys down there if they'll teach you some stuff.
Instead of looking for more land, look to improve your skill set. If you have land (which I know you do), learn to work that better. Maybe ask someone to come to the permission you have in exchange for some training? But then you'd probably be worried someone might oust you from your permission and take it for themselves? That's going to be a concern for the guys on here too.
Also, when everyone from 30 sites says no, start going further afield or trying different sites. My main site is a 15 minute drive away over the border into Devon. They have passport checks and all sorts down there! Hand scanners for 5 or 6 finger hands, and all that stuff. So even though I have a handful of places closer to where I live, I maintain them but really go to town on the one spot.
When you work 1 bit of land well, others will follow.
p.s. that's the nicest response I've ever given.
p.p.s. Asking to shoot on someone else's permission is the equivalent to going on a Porsche website and asking to drive someone's car. Very unlikely to get many people willing to take you up on your offer.
You can borrow my car for a shoot on your land mate lol.
I have asked the farmers who already have shooters if they would ask them if they want a tag along. I'm willing to learn off others and im old fashioned and would respect that they were shooting on there first if we were sharing land.
I drove out about half hour the furthest place from my house. Just no one wants to know. The land I have is empty. I did what you said and best I found was birds I'm not allowed to shoot. Yet the field on the other side of the woods is full of magpies. It's like there's a shield on the land that animals can't pass lol.