Nikon do a 35/2 which is a lovely little lens, but to get one for around £100 you'd need to go second-hand. In the case of the 35/2 I wouldn't recommend doing that because some of the older models leak lubricant onto the blades.
I think that 50 is still a perfectly usable focal length on a Nikon DSLR though.
The 50/1.8 and 50/1.4 are both excellent choices and I've seen optically very good but tatty copies of the latter go for around £100 used. While the 50/1.4 is probably a shade better from what I've seen of them, particularly in terms of rendering oof areas, the 1.8 is a very, very, good lens in it's own right and a ridiculous bargain even when bought new for the quality you'd be getting.