In answer to Les the sessions will be scattered across Leeds, most evenings have more than one to choose from, and the various pubs are listed on the websites. I have made use of existing sessions rather than try and set up new ones in competition.
As Willa says there is also an Irish festival next month, Irish music being very strong in Leeds. My wife went looking for music in Ireland, and was told she'd do better looking in Leeds. But although I have concentrated more on English folk there are some sessions included in the list that are Irish, and whenever musicians get together to play it's not long before Irish tunes are heard anyway.
The whole idea is to reflect the diversity of culture and talent in and around Leeds.