Hi @Jamie Finlay,
I cannot find any information online about a Swan SW158230b.
The nearest model number that I could find was for a [https://shop.swan-brand.co.uk/search?type=product&q=sw15840b|Swan SW15840b] and even then there is no online or downloadable user manual for it, which may have helped. (The Swan website shows no listing for your model)
The best that I can suggest is that you [https://www.swan-brand.co.uk/support/|contact Swan] and ask them for the information or for the user manual which should have the information how to enable/disable the Child Lock (aka Control Lock)