Hi Mate, I had this problem a few days ago, turned out to be the micro switch under the front brake lever. Look under the lever you will see 2 wires going to a small black plastic micro switch held on with 1 philips screw. Just remove the screw and it comes off, pull the wires off the switch, You'll see a sticky out bit on the switch that should push in and out when the brake lever is pulled. It should make a clicky sound if you push it with your finger. Got a new one off fleabay for about a fiver from Bike Business.
Good luck
Paul