I live in Matlock Bath and know how it works at the hotel.
The hotel do not want anyone other than the hotel users in the main car park opposite the front door of the hotel. Tradesmen are told to park to the right of the hotel on the old road, I have parked skips, vans and cars there on and off for years. this area is out of view from the hotel main entrance.
If you turn off the A6 and drive up the rising access road and then turn right there are plenty of spaces on the right. Do not go straight on at the top of the access road as that is the hotels private car park. Do not go left as there are allocated bays exclusively for residents of the houses on the A6.
Hope that helps.