Initial location
There is a large illuminated glass 'art wall' showing the "dark" side of the moon (apparently) here. Its best seen after sunset.
The puzzle
Look down and find the numbers associated with the words below to find out where the cache is.
The cache is located at N 51 ° A.B W 000 ° C.D
Black & White Eagle= A
B = E * F * G
Sweating Sickness = 1C8C
D = H * J
Expulsion of Jews = 12E0
Boudicca (d. - Royal Hatchet - Royal, Secret = F
Priory (Augustinian) = G23
Inquisitor Commander - Waterman's Arms = H
Great Stink = 18J
There are security gates at each end of Plantation Lane. These are locked at the weekend. You only need to go to the area east of the security gates to collect the answers.
If you want to find out about the art here there are large coffee-table books laid out for visitors in Plantation Place South, which is the building on the 'Moon' side of the alley. I'm sure that if you ask the security guard nicely they wouldn't mind you having a look if you're interested.