People who wish to cover their arms or wear Hijab are completely permitted to do so in the clinical environment. Obviously long sleeves would be disposable and changed as necessary, in the same way you would do so if you were wearing gloves. This is absolutely no big deal and I have worked with numerous people who would wear these as part of their working practice. It would also be considered completely routine and commonplace or expected in many other parts of the world.
Nobody should be discouraged from working in any clinical context because they percieve the above as being problematic, unhygienic or because some overzealous IPC nurse is going to make their life difficult about not being bare below the elbow: a policy that is far from total and apparently perfectly malleable when it comes to wearing a wedding band which apparently isn't an infection control issue at all.
The NHS rainbow is one of the things I am genuinely proud of and was glad to see appear in the press because it genuinely best encapsulates the spirit of all the healthcare systems I have encountered to date (I.e. rather a lot of them). It reflects the fact that the people who work in healthcare in the UK are amongst the diverse group of individuals anywhere and that there is no barrier for anyone to work in healthcare.
A person's individuality is an asset to health services, not a liability. The people working in UK health services are supposed to closely reflect the population they serve.