There's a club in Somerset - The Old Down Acoustic Club* - which manages to be both monthly (Fridays) and weekly (Wednesdays), and it seems to work very well.
Every Wednesday there's an open mic night, which is well-supported, with more than enough performers and some spare audience too, entry £1. Once a month on a Wednesday there's a special guest who gets 45-60 minutes (plus there are some of the usual floor performers); these nights are £2, get some more audience, and have recently featured Ember, Beck Sian, Sheila Chandra, Megson, Keith Christmas, and Jeff Gillett & Ron Taylor, among others.
Then there's a monthly Friday concert, entry £10 generally. These are also very well-supported, but with a mostly different clientele/audience, which is interesting. Recently they've had John Kirkpatrick, The Devil's Interval, Spiers and Boden, Vin Garbutt and Robin Williamson. Jez Lowe and the Bad Pennies are coming later this year.
So that's good for a newish (started in 2003) club which, though not quite in the middle of nowhere, is in a fairly small village well off the main road between Wells and Bath. It's a pretty big commitment for Johnny Francis and Cathy Judge, the organisers, but they always seem to be there (the occasional holidays excepted).
*It calls itself Acoustic as it is not strictly folk; it has its share of folkies but there's a lot of blues and other acoustic stuff. It also has several mics and a PA, and the odd bod has been known to plug in too.
*Also, it still calls itself the Old Down club, though it is no longer at the Old Down in Emborough, where it started up, but at the Kings Arms in Litton.