Portable appliance testing (in ANY environment) is NOT, per se, compulsory. That's confirmed on the website of the Health & Safety Executive:
http://www.hse.gov.uk/electricity/faq-portable-appliance-testing.htm
However there's a general legal duty to ensure that anything which is offered for sale to the public is safe to use, so PAT testing is regarded as the best way to comply with that requirement.
As an analogy, the majority of charity shops won't sell mains-powered electrical equipment because they've not got anyone to carry out PAT tests on such items. However I know of one charity shop in Stowmarket (which is run in aid of a major charity but not directly by that charity) which sells loads of untested electrical items. I think that they're mad to do so but, unless it can be shown that they've sold an unsafe item, they're not actually breaking the law.