You need to remember that while shooting at f1.8 might get you a shot in low light you'll have to consider that a) in low light and wider apertures auto-focus will struggle to focus, which means that with b) your depth of field being so shallow, only a small bit of the shot will be in focus.
The other consideration is that at 50mm, you won't get a very wide view, (remember that 50mm on a crop sensor is around 70mm film equivalent) and in tight crowd situations like in a club that might not give you enough space for a shot.
I took a few shots at a work party last week, and although I took my 50mm f1.7 with me, I used my kit 17-70mm lens more as it gave me more options to line up shots. I used a proper flash to fill out the shot and found that fine.
For example:
Kit lens, no flash. f5.6 40mm zoom on lens
hands in the air... by
AlistairBeavis, on Flickr
No flash, 26mm zoom f5.6
Horns... by
AlistairBeavis, on Flickr
Flash-auto fill, f5.6, 26mm zoom:
Salsa - Roberto Pla by
AlistairBeavis, on Flickr
So none of those were taken at 50mm (or anywhere close to f1.
, they were wider shots, and a wider shot can always be tightened with a crop.
It might be worth thinking about something different lens-wise.
If you're going to spend £300, why not this Tamron 17-50mm constant f2.8 ?
http://www.warehouseexpress.com/buy-tamron-17-50mm-f2-8-xr-di-ii-vc-lens-with-motor-nikon-fit/p1033482(I was going to buy one of these myself, but I found a Sigma 28-70mm EX f2.8 bargain on ebay, although I may swap it if 28mm isn't wide enough.)
I think a good option would be to hire a lens for an event and see how you find it.
