The profiles are manufactured in the UK to exacting German standards. All Rehau systems are tested by independent bodies such as the British Standards Institutes (BSI) and the British Board of Agreement (BBA). Quality control is paramount with all factories operating to EN ISO 9001 (formally BS5750).
You can be sure that window frames made from Rehau profiles will withstand all that the unpredictable British weather can throw at them whilst keeping the warmth in.