The things I can remember are:
- British author and set, mainly in the UK
- The main character (an ordinary bloke) is gifted a sandwich shop that I think is called "Sam Widges".
- The plot has similarities to The Illuminatus Trilogy.
- I'm fairly sure it too was a trilogy.
- It starts in the late 1950s/early 1960s
This is driving me crazy and any help would be most welcome!