Just replied elsewhere, don't do Stanmore.... go to Canons Park. Plenty of room and very quick getaway.
Cheers for that. I've just booked a spot 100 yds from the station on YourParkiingSpace for a tenner. Sorted.
I did Stanmore for the JPT, it was easy. Parked on a drive 300 yds from the entrance to the station. No pre-booking, you'll see folk stood at the end of their drives waving you in. We were back on the M1 in ten mins and home for 8.30am.