I have found that many tree surgeons are a good source of wood - depending on how much and how picky you are. More are now chipping stuff onsite to prevent needing to transport it but if you find a smaller one working locally they may well either let you know where they are working and you can help yourself. Or if really lucky even get them to drop it off (for a little something).
Since this wood has been removed for some reason anyhow and is 'waste' this is probably one of the best options. the brash is usually chpped down and left onsite for wildlife where this is apropriat. the other thing i would say is take what you can when you can get it. Admittidly this is not likely to work if you want to heat a whole house..
Theres nowt so queer as folk,
'cept for thee and me,
'n even thees a little strange