The Brentford Trilogy

Wikipedia contains spoilers

The Brentford Trilogy is a series of seven novels by writer Robert Rankin. They humourously chronicle the lives of a couple of drunken middle-aged layabouts, Jim Pooley and John O'Malley, who confront the forces of darkness in the environs of West London, usually with the assistance of large quantities of beer from their favourite public house, The Flying Swan, which is a fictionally quintessential British public house on a par with George Orwell's Moon Under Water, another famous fictional and idealised drinking place.

Amongst other characters are such gems as their mentor, Professor Slocombe, who is no slouch in the area of the magical arts himself, Neville the part-time barman, Small Dave the Postman, and Old Pete.

The novels in this series are as follows:

• The Antipope (1981)
• The Brentford Triangle (1982)
• East of Ealing (1984)
• The Sprouts of Wrath (1988)
• Nostradamus Ate My Hamster (1996)
• The Brentford Chainstore Massacre (1997)
• Web Site Story (2002)

In The Antipope Pooley and O'Malley take on the resurrected Pope Alexander VI the last Borgia pope.

The Brentford Triangle sees the pair thwarting an alien invasion of Earth.

East of Ealing forces O'Malley and Pooley to deal with a high-tech Satanic takeover of Earth by way of the Satanic bar-coding of the entire population.