I haven’t bought logs in around 7 years but just tend to keep my eyes on a range of different sources such as:-
1) Local staircase manufacturers for really nice mostly oak off cuts, but have to watch for excessive gluey sections.
2) Local timber yard, but not for off cuts more for the 4 x 4 packers they put between the packs, great for me, useless for them.
3) Have also sourced the packer type wood and various bent and twisted white wood from DIY stores.
4) Local arborists advertise in some places for fresh cut wood, just one of our local ones does, bit patchy but worth it if you can.
5) Good old freecycle, mostly in summer but an easy supply for a little time and fuel to collect.
6) Watch your local post office window for cards, have twice filled huge log store from old sources on farms etc where owner just wants their wood stock or logs gone asap (take wood saws with you if you do this, I learned the hard way).
Hope that little list helps.
James