I have a worcester bosch 280 combi boiler. Its installed on the ground floor. It works fine throughout the house- en suite shower, all taps, rads etc apart from the shower in the loft (2nd floor). It always cuts out (i.e. water goes cold but no difference in pressure) for 30secs to 1 min halfway through a shower. I had the pressure at 1bar and increased to 2 bar just in case this made any difference which it doesn't. Any ideas??