The Westwood inn is listed on the stopover map, looks ok and has feedback.
However I have not used it yet!
I have also stayed in the truckstop at the side of the A38 in Ivybridge, which served a purpose.
However have you asked at the wedding venue?
We have taken the motorhome to probably 9 weddings in the last few years, always been given a spot to park in for free.
Even at Nottingham Forest Football ground, they even bought an electric lead out plugged in, without being asked.