This Cache
The cache should be fairly easy to find. You're looking for a Film Canister, so don't forget a pen or pencil.
About The Hitchhiker's Guide to the Galaxy Building
Megadodo Publications are the publishers of the wildly popular Hitchhiker's Guide to the Galaxy. Ford Prefect was employed by them as a researcher for the guide. It is one of the great publishing corporations of Ursa Minor. It is the second hippest place in the Universe.
Congratulations to Dawes Scorpio and Brookomatic for the FTF!!
Approaching this cache from #29
Sit on the bench at No. 29, and head north up Narrow Lane Clieves Hills (the way you face when sat on the bench), and then right through the gate on the Public Footpath (and yes, through the garden). Follow the path to the cache.