i think you can get individual beds in that joiners shop spunkhouse if he's not fully booked.
There's also a/some bunkhouse/s at annstead farm between seahouses and beadnell. I think there's one in wooler too.
its worth going anyway just to stay in the turkey hutch
Try this place http://www.surfshacks.co.uk/windy-gyle/ It's in Belford, just down the road from Bowden. I stayed there about 10 years ago and found it perfect.