We're close by and I used to stop off there quite often. I must say, I wasn't been aware of any ill-feeling towards cyclists whenever I visited. However, I stopped riding that way for a while but I was aware that the gate had been closed. Sometime last summer I rode up to the gate to see if there was any way to get in by foot. It was properly locked, but as I stood there a lady came along in a little buggy and explained that if I wanted to get in, I would need to be a member, and she explained - quite pleasantly - the various membership options, which were all far too pricey if all you wanted was a cup of tea and a snack. I agree that it is/was a great place to stop, and being able to see the planes up close and flying around was a bonus. If it's open to cyclists again then that's great.
The little cafe in Southall is still going, but I think that they've reduced their opening times. They never seem to be open when I go past, but then I was never a big fan anyway because, in my experience, the food wasn't very good.
But there's a new cafe, set up specifically for cyclists and walkers, called the Cowshed Cafe, at the top of the hill between Northill and Cople, which I recommend - very friendly, start-up, business of the type which deserves our support:
https://www.thecowshedcafe.co.uk