Erle is an Australian chap from Sydney, probably our most famous martial artist if you don't count boxers. Unfortunately his reputation is not what it could be, mainly due to his obsession with Dim Mak I think, though money might also be an issue.
I found an interesting taiji family tree (similar to one Xue found for me about bagua). In it Erle is listed as a student of Chang Yiu Chun who was a student of Yang Shao Hou, a student of Yang Jiang Hou. On his website he also claims to have done some training with Fu Zhongwen and Yang Sau-chung, the son of Yang Cheng-fu. I don't have a clue as to where he learnt Tung's forms.
As far as his bagua is concerned, it appears to be Gao style. His teacher being Ho Ho Choi, a student of Gao Yi Sheng, who was a student of Cheng Ting Hua.
I have seen him perform both taiji and bagua first hand at a seminar I attended (I didn't have to pay so I went). I found all his forms to be afflicted with short, often jerky, movements which are supposedly demonstrative of fa jin and, of course, Dim Mak.
I don't really want to bash Erle as he seems to be a nice enough guy, its just that some of his stuff is, well strange.