Regarding the distance, I don't always rely on the GPS Track but my GPS unit is kept in a Montane Atomic DT compression mesh bag, so it's outside and 'unshielded' all the time. We also went past Hollins Cross, almost to the foot of Back Tor and back, which should account for a quite a bit of difference.
Sometimes the GPS track is so erratic though so I essentially have to redraw it by hand based on what we did. You can tell on my reports if it's a red track then it's GPS, if it's blue I had to redraw it in Memory Map. So Blue would probably be more accurate generally.
As for car parking, in the summer months you'll often find the overflow car park by the train station is open. It's £4 a car and you deal with a genuine human being so no chance of getting ripped off. It's worth checking if this is open.
It looked like a great day out. Glad the weather held as the forecast was a bit well maybe it will maybe it won't.
