You can fill self employment pages on a self assessment form in 10 mins, very simple once you have info at hand. The driver does all the donkey work working out expenses, put income in one box, expenses in another and deduct for net income, personal allowance is £11500, if unsure ring helpline and make a note for future years.
Paying a professional could pay for itself many times over if you're not financially minded and able to ensure you get the deductions correct (and all of them).
I'm numerate and find it easy but, for example I can't paint a picture or draw (and am in awe of anyone who can). It's very easy for those of us who find numbers easy to not appreciate how difficult some others find them.