I'm using Williams Rochdale, just a couple of miles from home so pretty convenient - although I'd be much happier if I only had to visit once-in-a-service-interval while.
No update yet, it's booked in for next Tuesday, 11th June. Everything crossed things will get sorted.
As part of my home-brew diagnosis I tried switching to BP Ultimate from V-Power Nitro - FWIW my commute mpg has improved, currently at about 36-37 from about 34-ish. Might just be coincidental with the change in weather