In reply to Fraser:
the D700 is a great camera and much more sturdily built than the more recent nikon bodies like the d600/610 and D750. They're going for less than £500 in good condition second hand from shops that will give you a guarantee at the moment, which would leave you a decent amount of change from your £1200 budget to spend on lenses.
If you shoot action/sports a D3 might be worth a look too - essentially the same camera but more FPS in a bigger body with a vertical grip that's sturdier again.
Both are significantly heavier than the newer cameras, have less pixels and don't do video. On the plus side they do more FPS (MBD10 grip needed for D700 for this, about £50 second hand now) and have dedicated buttons for AF (most of the newer cameras ditch these for video controls).
I have a D700 and have made bigish prints from heavily cropped images - the bigger the print, the further away you stand when you look at it so pixels aren't as much of an issue as you'd think. Nobody apart from you will look at your pics at 100% on a monitor. 12MP to 24MP is only 1.4 times more resolution in each direction so the difference isn't as big as it sounds. Having said that, if you take a lot of landscapes more pixels is never a bad thing and it could well be worth going for one of the newer, slower handling bodies.
Lens wise, what do you use your ultrawide for? I find that apart from landscapes under stars and estate agent style pictures of the inside of houses, absolute field of view isn't a huge consideration. Small changes in focal length at the wide end do make a big difference to FOV, but a bigger difference to the price!
I've had the 18-35 AF-D (good lens, and I believe the newer G version is better) and the 20mm 1.8 g - these are more than wide enough for the vast majority of my "regular" photography. For when I need the biggest FOV I can get I compromise on IQ and distortion and use a cheap 16mm fisheye (180 degree diagonal) which gives a bigger FOV than almost any "regular" lens. Obviously, you might be shooting something that needs low distortion and good edge performance, so it might not be the way to go for you. However, if you can compromise, it's cheaper, lighter and some would argue more versatile than getting "one ultrawide to rule them all" - the 20mm and the fisheye together cost me less than the 16-35 would have done, goes wider in absolute terms, and lets in a lot more light.
If you don't mind selling them again afterwards, you won't lose much money on a second hand lens (as long as you don't break it!), it's worth experimenting - I bought my 18-35 to see what I wanted from an ultrawide, got two years use out of it, learned a lot, got some pics I really liked and sold it for £25 less than I bought it for.
Hope that helps. Whichever way you go, enjoy your new kit!