I am assuming your turnover is under £16.500 for your first year. No need whatsoever for any accountant at this stage.
HMRC will shortly send you a return form. You only need to be concerned with the orange sheets (everything is colour coded) for self employed.
It's all very very simple. You fill in, in the appropriate box your expenditure, and you fill in, in the next appropriate box your takings. You then subtract the expenditure from the takings to find your yearly profit and this goes into box three. Capitol allowance is a bit different but the forms clearly guide you through this part. Sign and date it and then send it off. HMRC will then tell you how much if anything you owe, normally to be paid before January 31 st of the following year.
The longer you stay in self employment the more slightly complicated it becomes but for now in your first year.....it really is simple. The system is designed to help you and to make life easier in your opening years.