After doing some more research I'm seeing that my transmission temps are over what is recommended for running an automatic box at yet I think the temps I'm seeing are what other people will probably see on an X5 5HP-24 box due to the design of how it's cooled though a heat exchanger that's ran off the coolant radiator via a thermostat. The engines in our 4.6is seem to run at a very high temperature of around 105-108degrees - with this in mind the transmission is going to struggle to run at much under this.

Couple of links that are quite interesting..

Transmission Oil

Don’t Let Your 5HP24 Automatic Transmission Overheat

The majority of people seem to say that 200F (93C) is the maximum it should regularly see. This ties in with mine misbehaving at much over that.

Anyway....it's enough for me to warrant installing an additional external cooler to bring the temperatures down to a more acceptable level, especially when towing. Even if it doesnt fix the 2-1 problem, (although I think it will) it will help with the service life of the new fluid that's in there. No wonder the X5s are so prone to gearbox issues with such high running temperatures. Also ties in with the 4.8is being much less affected with their 6speed boxes and newer engine management systems since their coolant typically runs around 20-30degrees lower and thus so will the transmission.