Existing in its present form since 1993, the CE marking is a key indicator of a product's compliance with EU legislation and enables the free movement of products within the European market. By affixing the CE marking on a product, a manufacturer is declaring, at their sole responsibility, conformity with all of the legal requirements to achieve CE marking and therefore ensuring validity for that product to be sold throughout the European Economic Area. See more at gov.uk.
The TUV Rheinland GS S1 certificate is a certificate presented to manufacturers as the de facto certificate for acceptance into Europe. The certificate can be considered the de facto certificate because it not only demonstrates full compliance with the GPSG (German equipment safety law) for Germany, but it also demonstrates compliance to the LVD (minimum EU requirement). Link to TUV UK contact details.