Just incase anyone gets this worth checking your banjo bolt washers. I had the red flashing brake warning on the dash come on and spongy brake pedal. I got it home and feared new caliper/piston. On closer inspection one of the washers on the banjo bolt had totally corroded away and fluid was leaking, so replaced with new copper crush washers and topped up fluid and holding fine now. 17mm OD, 12mm ID size of washers I used.
