James
Not sure what level of experience you are or what type of diving you do or how much other kit you have.
However, if it is your first torch I would seriously look at the DR4 before investing quite a bit more in others. It is very robust and can manage a few knocks and is generally a good all rounder for UK diving.
I have both the DR4 and the DR8 and whilst the 8 is brighter it is heavier and more cumbersome.
I would concentrate my dosh on other bits of kit (eg twins, wings etc etc) before getting a F.O. Mega torch. However if you have all the other kit, then I would go down the umbilical light sabre route
Simon