You are able to file a Self Assessment tax return for yourself.
If you are self-employed, you must register for self assessment by following the following link:-
https://www.gov.uk/register-for-self-assessment
Once this has been completed, you do not need an accountant to file your Self Assessment, however, it is advisable to seek professional help in order to be sure that everything is correct, and that you are claiming for all the tax relief on your return.