As MyShowcase Stylist you are an independent agent; the owner of a business.
In the UK, the tax regulations stipulate self-employed registration by everyone who starts their own business. This should be done within 3 months of the start date, and a £100 penalty can be applied for failure to do so.
Registering yourself as self-employed is really easy, just go to the HMRC website (www.hmrg.gov.uk). If you have any questions call them for advice during business hours on 0845 915 915 - they are really helpful and friendly.