I think it would be very awesome if you spend at least 1,000 of those pounds on something completely inane, just because you can. Like getting a shit-ton of R/C cars and helicopters and stuff. Electronic gizmos and crap. Need a new kitchen knife? Get a super expensive professional knife, then get the rest of the set. Get a deep-fryer, because deep-fried stuff is delicious, and don't even try to deny it. I noticed that I'm forever low on one utensil or another between dishwashings. So buy 15 of each, because you WILL need that many spoons. Get the expensive foodstuffs, the good detergents, the good EVERTHING.
Walk into your local grocery store and GO NUTS.
Go to Newegg.com and GO NUTS.
Go to ANYWHERE AND GO NUTS.
Road trip of Europe. Do it.
I'd recommend hitting some of the USofA, but wait until at least May or so, because Winter sometimes sucks a bit depending on where you go. Still, Vegas and most of California are nice, and Wisconsin in the late Spring/early Summer is one of the best places in the world to have a road-trip, IMO. Also, Chicago, Illinois. And Louisiana. Maybe Miami, if you like that kind of thing... The list goes on.
But yeah, definitely put away a large portion - say, 1/3 or so - into some kind of long-term savings plan, because hey, shit happens. My father got laid off at the age of 52 a month or so ago, but my parents had a great big nest-egg (I think that's what they called it) of savings that kept them comfortable and somewhat worry-free for the few weeks of unemployment.