I've started it recently, and I've found that it typically involves a bit of detective work in each location; I'm not sure whether that's deliberate. In particular:
* Cornwall #4 (Poldhu Point). This is at the bottom of 2 steep hills. When you get to the beach, you have to follow a flattish road along the coast, past the retirement home. Don't do what I did, which is to climb up the next (huge) hill, then realise that you've missed it!
* Cornwall #5 (East Looe). The sundial is mounted vertically rather than horizontally, so you may walk past it without noticing.
* Cornwall #6 (Callington). The Old Clink is supposed to be next to the church. However, I couldn't find the plaque they were talking about. As far as I can tell, it's now been converted into offices, so you can't wander inside. I just took a photo of my bike next to the front door, where there's a sign up saying "Rent a unique office space at the Old Clink". Hopefully that will suffice.
* Devon #4 (Lydford). The tomb is outside the church, but the stone tablet (giving dates etc.) has been moved inside the church, so you won't be able to see it when the church is empty (locked up). Fortunately I arrived at the end of bell-ringing practice, so I was able to get inside. The stone tablet is hard to read, but they sell cards for 25p with a copy of the text, so I recommend buying one of them.
* Somerset #1 (Ebbor Gorge). Another monster hill! I couldn't find the plaque they were talking about. There's a sign in the car park, and a mini pavilion a short walk away with signs all around it. However, neither of these has the relevant information. The BCQ document says "Check is down track from Car Park. Not visible from road." That first sentence is barely English, which doesn't help. There are 3 tracks (walking routes) which lead away from the car park, of varying intensity/length, e.g. there's a 1 hour route with lots of steep climbs. I don't know which track you're supposed to follow, or how far you have to go. I didn't really want to leave my panniers unattended, but I also didn't want to carry them around with me, so I just took a photo in the car park.
* Surrey #5 (Box Hill). The view point is a semicircular wall on the side of the hill. There are arrows carved into the stone, with distances, e.g. "Gatwick 5 miles thataway". You need to look at all the distances to work out which place is furthest away. However, it has started to erode, so I'm not entirely sure that I got the right one.