Anecdotally, so far Cardiff seems to be a likely spot for an actual instance of someone having to queue due to a free stall being inaccessible as a result of non-Teslas using adjacent bays. There’s a picture on TOUK of a Tesla, Audi and BMW all charging at the same time. Adjacent bays aren’t pictured but if unused then 5 stalls would be “available” but only 4 accessible. I think this is how the brave new world is meant to work, I.e. there’s no suggestion the two non-Teslas are doing anything wrong by using an adjacent space due to the position of their charging port.
Not worth asking permission to post the pic here as there’s no evidence anyone had to wait but it does sound like a number of non Teslas have visited to test out the newly available chargers.
At least this site, being a Service Centre, has Tesla staff on site during working hours & I’m sure they’ll be made aware of any queueing issues should they arise…