We've been renting a new place since Christmas. Landlady was asking £1400 pcm, we are paying £1250pcm, plus she put in laminate flooring throughout downstairs on our request (carpet was extraordinarily manky). We did specify a year's no-break contract, but she was keen on that too.
We have always been quite, er, ambitious with what we have asked for though. When we viewed our last place we said it would need too much work and weren't going to offer, but it turned out the landlord owned a building company too, and asked us to tell him what we wanted done. So we came up with a list: new floor throughout, repainting, knocking wall down between living and dining rooms, new appliances and cupboard fronts in kitchen, returf garden and put a shed in. He did it all and agreed to £100pcm off the asking rent (this was 3 years ago).
Obviously it depends on who your prospective landlord is and what is important to them. Play to your strengths - have they had sharers in before who have caused probs with neighbours (ours had)? So would probably be keen to get a family. We told our landlord we were very boring and didn't have loud parties into the early hours (true). If you can get great references, say so straight away.
So the moral of my story is, you can't lose out by asking! All they can say is no. Our philosophy is to ask for everything we want up front, at the point where we have the most power, and then once agreed we just get on with things and cause no trouble in return. IME it is much harder to get anything once you have signed.