At WP1 you will find a plaque with a date on it.
To find the GZ coordinates multiply the second number of the day by 11 and add 1.
Add this number to the south coordinates.
Add all of the individial digits, multiply that number by 11, then subtract 5.
Add this number to the east coordinates.
Checksum S 18 E 25
The cache is a 1ltr Sistema container with plenty of swaps.
I hope you all enjoy this little bit of a foray through my childhood playground.
Watch out for joggers and people walking their dogs.
*** First to find honours go to JezzzaXtreme ***
Note: After creating a bit of frustration for SecretSquirrel-BJC I thought that this little note might be prudent. The puzzle can be worked out two different ways, but only one of them will help you out in the field.