Probably (and restricting myself to folky stuff):-

Side 1 of 'The Gypsy' by Mr Fox ('The Gypsy' and 'Mendle')
'The Shipbuilder' by Bob Pegg & Nick Strutt (I know it's an album but it's also one continuous piece of music)
'The Alchemists and the Peddler' by Dransfield
'Matty Groves' ('Live at the LA Troubador' version) by Fairport
'Fair Fortune's Star' by Carolanne Pegg
'Tam Lin' by Jumpleads
and 'Famous Flower of Serving Men', 'The Death of Young Andrew' and 'Jack Rowland' by Martin Carthy

(I like long songs!)