Screwfix do a good Honeywell Pressure Reducing Valve (15mm or 22mm available) which can help tame the whole cold water system.
http://www.screwfix.com/p/honeywell-pressure-reducing-valve-with-gauge-15mm/69396
http://www.screwfix.com/p/honeywell-pressure-reducing-valve-with-gauge-15mm/69396