Many small businesses I know use Sage or a similar small business targeted software (Sage edition targeted at small businesses) to do most of their accounting. Then, after checking the accounts they may pass it to their accountant to finalize it and file it, though these businesses are processing much much more than £3000 a year, but they are still small.
Depending on if you will be self-employed or not you may have to look into declaring yourself self-employed and paying the respective taxes or national insurance contribution.
You may be able to do all the accounts yourself if you are a Limited Company; though an accountant can advise you on your accounts and related filings if you decide to get one; which can be a big help than trying to learn everything yourself.
P.S. If I accidentally got something wrong there; please feel free to let me know.