Exeter services seems one of the best around, 32 Super chargers, 24 gridserve.. rocked up on Friday 22nd when everyone was travelling at 6pm and plenty of both free..I dropped into rugby services just before lunchtime today, Christmas travel was in full swing and it was very busy.
Both Tesla and Gridserve had one unit down (I’ve not actually ever seen all 12 gridserve units working) which is less than ideal.
Tesla had 2-3 of their 28 slots free for the 15 mins I was there. The charging speed was okay but not amazing, I expect we were up against the site power limit but the turnover of cars was good.
Gridserve consistently had 4 cars waiting with a martial managing the queue.
It would have been messy without those additional 16 Tesla units put in earlier this year and it soon will not be long before they will need more in the area.
It was our first 'supercharge' so can attest it's by far the easiest charging experience I've ever had, and even lower rates (£0.55p/kwh).. however, had we been in the ID.3, the gridserve setup was pretty good, albeit it, very expensive.
Scary things with Tesla, looking at the telemetry available via their API (I installed Teslamate on my Unraid server), it has full GPS coordinates, and everything else logged, tyre pressures, even outside/inside temperatures etc.. it's all a bit intrusive?
Here's a 150 mile trip:

It seems to be approx 8 to 9 second averages for the entire trip.. crazy..
It's our first Tesla, and overall, very impressive.. but not without fault.. namely we have named the car Wussy.. since TACC is so nervous.. and having the newer firmware with the 'recall' software behaviour for autopilot, it's 3 times more restrictive than our ID.3, if you dare look at the speed or your mirrors in the first few seconds of engaging autopilot you get a warning to pay attention to the road.. way too draconian IMO.