Hiya
This has been discussed a few times, if people are anything like me, they probably still use the same suppliers. There are some threads at the top of this forum, which list good suppliers, which should give you some direction.
http://www.healthypages.co.uk/forum/showthread.php?t=18843
http://www.healthypages.co.uk/forum/showthread.php?t=88
Hope that these help, there are other posts in this aromatherapy forum, but these two are probably the most useful.