the little plastic thing in the fluid pot is the float. when there is no fluid in there it sinks and the brake light comes on on your dash. the handbrake light (!) is prbably coming on because of a faulty switch. when your driving wiggle the handbrake lever and you should see the light flicker or maybe gone on and off. i've had this loads of times and spraying wd-40 or electrical contact cleaner on the switch normally sorts it. it gets sticky with all the mcdonalds and fag ash falling round it over the years!!