I think it depends on what sort of a business you have.
If you are a mobile therepist or work from home then yes, doing your own accounts is very straight forward.
If you have a salon, work with someone else or have staff then you should look at having an accountant.
Finding a good one can be the problem. A good one will say, did you know you can claim for xxxxx a bad one will just take your figures, put them in the boxes and submit your form. Only difference from you doing it yourself is that you've just given them £300.
I've had the bad one. Then my husband started doing my accounts for me and I haven't paid tax since, he claimed my salon clothing, my ongoing training fee's, my fuel costs, and loads of other things that I'd never thought of.
Which ever way you go, my golden rules are, get a receipt for everything and write on the back what it's for and the date. Even a week later can have you wondering what the heck that was for.
Also if it's not claimable, you'll soon be told so, but the tax office won't tell you what you could have claimed for.
If like me, you take one look at the self cert form and wonder what language it's written in, then get a book keeper, word of mouth is as good a way as any to find a good one. Just make sure you put your return in on time, there is a fine for putting it in late and you are unlikely to get that appealed.