Hiya, Your brake warning light is trying to tell you something's wrong. You say you've checked the brake fluid. When you take the cap off, make sure the float inside is free to move. Move it gently as it's fairly fragile.
If this is OK, then it could be your brake pads are worn down. They have a sensor inside the pad which brings the light when they wera down. Either check them yourself if you feel able. If they're down to about 3mm of pad material, change them. Change them all both sides, not just one side. Get a good make, don't feel tempted to go for cheap ones. If you only do one side, your brakes could be uneven. If you do it yourself, be careful when you jack the car up. Use proper axle stands underneath. Also, try and refit the tyres in exactly the same position on the wheel as they may be off balance if you move them round...mark them with a bit of tape or something. If you don't feel able, take it in to a good garage or one of the Quikfit places. Ask to see the old brake pads when they change them.
That should solve the problem.
Best of luck.
Denis (CarAid mobile repairer)
Denis Langley
November 2007