SP,
I do not know of any at this moment. But I will see if I can find out some info for you.
It is interesting to read that the Aussie Firms may not consider them large enough. They are due to enter the FTSE100 in September, at current sp they would sit around 80th. You might get a nice surprise if you asked some of the Aussie Companies about margin lending against Tullow based on the above data
regards
Acamas