You can work in as many fields as you like. Each field will need a separate self-employed page in your annual Tax Return, but you only need to submit one Return.As far as HMRC is concerned, you can use what business name you like. You don t have to use same business name on website, although you would probably find this more convenient. If you don t notify any other business name, HMRC will assume you are using your own name, you don t have to trade under any other name.
1. you can trade under your name i.e. business name = Mr Joe Bloggs2. you can put the kind of work as network engineering and graphic design then you only need to fill one section on your return