The British Equestrian Trade Association represents manufacturers of equestrian related tack, clothing and equipment. It is involved in the development of industry standards for these products. BETA has collaborated with the Pony Club on a new Equipment Safety Badge. Their website carries many helpful guides explaining the purpose, construction, standards and care of protective equipment. See below.
The British Horse Society website gives extensive guidance in its Riding section – including getting started – and also the Riding Safely link to horseaccidents.org.uk which covers Advice and Prevention.