Lots of guys do their own return, but I personally think that a good account is worth their weight in gold if you get a good one. There is bound to be plenty good single operators working local to you that you could have a chat with.
The idea of self assessment marra is your supposed to be able to do it urself but tbh het urself an account- a small 1 man band rather than a big company & ask for a fixed fee....as a single self employed trader you should find someone local circa£300-500 depending on how much info such as receipts & cis certs & your married status all depends as to how much you could get back. But an accountant will know all the additional things you can claim on that you may not of thought about eg:- %of use of your home as office for instance..
Avoid the companies that want a% of your return ....theyre just a con