Ha dthe same problem with my XeDi. Brake switch has been mentioned in other threads so it's worth checking however, my problem was the wheel sensor on the front right. Each sensor is push fit into the hub and can work loose slightly which increases the air gap. If this happens you will get all three lights on the dash. If you can disconnect the multiplugs for each sensor and measure the resistance, should get about 1 - 1.5 KOhms. If you get this the sensors should be OK. Then pull each sensor out of the hub in turn and clean (DO NOT HIT OR SHOCK THE SENSORS OR DAMAGE WILL OCCUR). Push back into each housing after coating with anti sieze, making sure thay are as far in as they can go. After this drive off and all lights should go out when you reach about 5mph if this was the problem.
This may sound long winded but would be my first check which could save a lot of money.
Hope this helps,
George.