Hello chaps,
I'll try not to get too technical, but here' s a bit of info on torches.
The one OMD has is indeed the one in the link. Very good value for money but you're paying your money and taking your chance as some leak. One way to reduce the chances of this is to take a coil off the spring in the head. (The batteries for them come in 2 length depending on whether they've got a protection circuit or not, in trying to accomodate both lengths the spring is a bit long when used with the longer protected batteries that the torch comes with and it can put pressure on the bezel when screwed up.
"Cree" is a brand name, there are lots of different cree leds. Indeed it is often used when Cree are not involved, as is the case in the torch in the previous link. It uses a P7 led which is made by a company called Seoul, not Cree. Cree's equivalent is the MC-E, and indeed you're better off getting the MC-E version of the same light:
DealExtreme: $95.00 Diving Cree MC-E (K-WC) 3-Mode 640-Lumen LED Flashlight Kit (2*18650/4*CR123A/4*16340)
Don't be put off by the lower lumen rating, I've compared the two side by side and it's actually very slightly brighter than the P7 in use due to the reflector being better suited to the form factor of the led, and it will have a slightly better runtime.
But, you take a risk ordering either. Support and backup is difficult at best so if it dies you're looking at a DIY fix.
If you want to spend a bit more and have a greater chance of it lasting the Shockwave LED is a good buy. Good for the price, long runtime, make sure you get the more recent version, it's got twice the output of the original.
Either of those will make a Frogman look like a birthday cake candle!
That said, a light cannon HID for £60 is a bargain, the hids are not that fragile as long as you take a bit of care with it, and if you don't like it you should be able to make a decent profit on it on Ebay!
Hids are generally better focused than leds still, it will penetrate murky water better as the beam is more concentrated. Leds will generally light up more of the seabed around you but the downside of that is backscatter from light reflecting off particles in the water.
Hope something in there helps!