Some people claim that Stone Street is the narrowest named street in Britain. According to my measurements it is just 28 inches wide at its southern end. Just enough space for one person to search for a cache...
By the 18th century, Prescot was full of little cut-throughs like this, but now Stone Street is the only one left. Probably created as a boundary marker between properties in the 1550s, the street developed into a route to a medieval windmill.
(Other people say that Parliament Street in Exeter is about 3 inches narrower, and although they may be correct, let's pretend they're not.)
You are looking for a nano cache (well, nothing else would fit would it?). You'd struggle to get a wheelchair or push-chair to GZ.
There is pay-and-display parking at the much wider northern end of the street.