The usual case with a ceiling rose and the wire arrangement you describe is as follows...
The red wires are permanent live - one is live coming in - one is live going out and one is live going to the light switch. They connect together and to nothing else - they do not connect to the light.
The black wire that comes back from the switch to turn the light on and off is switched live - it is usually marked with a red or brown sleeve to show that it is sometimes live and potentially dangerous. It connects to the brown wire of the lamp.
The other two black wires are the neutral return path - they connect together and also join with the blue wire to the lamp.
The earth conductors should connect together and also to the body of the light fitting if it requires an earth connection.
Your challenge is to identify the black wire that carries switched live back from the switch.
If you're not using a conventional ceiling rose then you will need a 4 way terminal block up at the ceiling to make the necessary connections.
An electrician will be able to solve it for you quite quickly.
Take care - good luck...
Peccavi
January 2011
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix lighting.