eBay.co.uk: Custom Divers HID,umbilical dive torch, light,, diving (item 120032989250 end time 24-Sep-06 15:46:30 BST)
I don't know how the above fits in with your plans time wise.
One thing to consider is that a dive light is a fairly hefty investment and spending up to £250 now to get a light that you'll want to change again when you have more money might not be such a good idea?
NiteRider (USA) do a good light - I have the double header (12½/25 watts?) -
///:::...NiteRider Dive Lights International...:::\\\
A very tricky choice to make.
Also, why do you especially need 2 hands in Scapa and not want to use your usual light?