The business in question is owned by me and I'm the only employer up to now.

I've got a website but its not set up yet and won't be for a week or 2 but I've already started emailing clients.

As of now I don't have any customers so there's no money coming in. Its also all done online, there's no need for a premises as the products are all made to order from another company I'm affiliated with.

Cheers for any help.

Whether you have to register depends on local laws. Generally you don't, except if you will need to collect local sales tax.