@Rosie I use one very regularly - at least fortnightly and more often weekly. I use it as a space to train for Rally so I can set out a course without being interrupted but most other people use it to exercise reactive or untrained dogs. It is also block-booked by a cople of dog trainers for classes. It's always fully booked, not just during lockdown. (There is a large field, a barn and an outdoor sand-school.)
The one I use has a very trusting system for payment- you just put your money in an envelope and post it into a box with a slot. To book they have the field and barn diary online, on both facebook and website, and so you check available slots and then text the owner to book. I used a different place once where you had to pay in advance by either paypal or bank transfer which was fine but I haven't been back because there was no parking other than the (narrow) road alongside the field. The one I use regularly has ample safe parking.
There are strict rules about keeping your dog in your car until the previous people have put their dog back in their car which is good and also obviously picking up poo - but there are plenty of bins so this is easy.
There are a couple of porta-loos which is a bonus and coffee machines which you pay for. Oh yes and seats for the owners (I never use these!)
One of the most convenient things for me is that there is a water supply so I don't have to carry it with me.
The owner used to supply balls and dishes but because of Covid now asks you to bring your own.
There is some agility equipment in both field and barn.
At the moment there is hand sanitiser and cleaning spray - so you are asked to clean the bits of the gate you have touched on exit.