All lights are out in first floor bedrooms. Have a Mk sentry consumer unit. Turned off mains, switch is up for \\\'upstairs lights\\\' still no lights. Checked all ceiling light fittings and found one bulb \\\'catch\\\' on the fitting -don\\\'t know correct word, sorry!- is slightly broken, leaving the bulb at a slight angle. Could this be the problem causing a short circuit? What do I do next?