You'll need professional indemnity insurance. You also need to bear in mind that there will be no paid annual leave or sick leave or employers' pension contributions. And absolutely yes to an accountant - as well as your own tax return, there will be corporation tax (assuming you're going down the ltd company route). It can work very well - my DH has done it for years.
Just a quick reminder that you can offset business experience for tax reasons, e.g. the laptop, screens etc. Friends of mine who do this don't bother with health or life insurance, but obviously that is a risk. An accountant used to contracting is a great idea.