What's wrong with my plant?!

It is a Dracaena Massangeana I believe.
Usually the leaves turning brown just at the tips is caused by lack of humidity, but it looks to me like that is not the case with yours, my guess is that it has too much water. Is it sitting in water? When you water does it drain completely, or does the saucer still keep water sitting in it? Dracaenas do not like to be in standing water, but do like moisture in the air. Try after you water it pouring any water in a saucer away and letting it dry a little before watering again.

Hi, thanks for getting back to me.

Hummmm when i noticed he was all brown I gave him more water.... maybe not a good idea.

He lives in a big brown pot in the hallway. The pot does not have a hole at the bottom and water can not drain away (as its sitting in the hall on wooden floor). I watered it today as the soil was bone dry, I do admit I hadnt watered it for a while.

The hall gets quite a bit of light, theres a radiator in the hall but my house is never really hot only ever warm.

I have a Yaccka (sp?) in the same pot in the living room and thats fine so I have moved it in there to see what happens but it looked so lovely in my green hall and seemed happy!

Okay! Well now we can see a problem, if this pot it is in has NO drainage holes at all that is the problem. All plants have to have a drainage system so that water can be carried away from the roots, without the holes the only way for the water to get away is by evaporation and that means water will collect in the bottom of the pot and be very slow to evaporate, so while the top few inches of soil are dry the bottom of the pot is soaked. The best way to have a plant indoors is in a pot with drainage holes and set that pot into a decorative pot without holes, after watering you pour off any water that has drained out into the decorative pot and it keeps your floors safe. The Yucca you have in a similar pot has a shallower root system and needs less water, so it may not be showing any ill effects yet. Was the plant in a drainless pot when you bought it? I find it hard to believe any store would sell it that way, unless the sales people just do not know about plants. If that is the case I would take it back and complain.

Hi there, another problem you have is central heating, although it may not be hot, it will still dry the air - and as Wohlibuli has pointed out they like humidity and not too much water at the base, they do like some light, but in all honesty humidity and good drainage are far more important than a lot of light, they would do far better in the bathroom even if it is not so light. and i do agree you defo need good drainage, another sagestion i could make, is instead of watering the pot, i had several of these in my flat, and once a week i would take them out of the decortive pots, so just in the plastic pot with holes stand them in the shower, give them all a good sprinkle with cool water and leave them there for an hour or two to drain and them put them back in the decortive pots, in the summer i would put them out in the rain to get a bit of water on there leaves, they used to really like this. your only chance of saving this plant now would be to remove the pot and take away much of the compost around the root ball, re-pot in fresh compost in a plastic pot with drainage holes, remove any damaged brown bits and keep your fingers crossed. good luck.