One of the cons you haven't mentioned with the 7900 is that the chainrings are designed to blend with the crank and although aftermarket chainrings will fit, they'll not look great. In the UK 7900 chainrings are ridiculously expensive so its something to consider if you might wear out the rings quickly.
If you're thinking silly money (Vuma, Storck, THM) then the THM Clavicula cranks for me are a no brainer. Very nice piece of kit. If you want to be more sensible then I'd choose Red, followed by 7800 (yes the older one) then Record, then 7900.
Last thing to consider as you live in the UK is availability of parts. The three pricey cranksets all require patience in sourcing spares where as Sram and Shimano parts are readily available (Campag not so much)
I did consider this slight issue about the 7900 crank, especially since I use larger chainrings and am definitely not willing to pay the premium which you pay for the DA chainrings. I would go for the 7800 but I don't like the look of them. At the moment, I'm considering an FSA crankset as a temporary measure, mainly because they look good. Either that or an SRAM crank, same thing.
I'm not really too keen on the Record crankset as it'd clash with the rest of the bike, being a Dura Ace build.
At the moment I'm thinking, temporary, cheap-ish, carbon crank like FSA SLK Light or an SRAM Red and then eventually get either the Zipp Vuma or the Storck Powerarms SL.
So, for now, can anyone give me their opinions on the FSA and the SRAM cranks. Main issues again are durability - I'm willing to take the slight weight penalty for the time being.