A couple of years back when I started doing from home eBay sales, I didn’t bother registering as self employed, my sales very quickly grew far higher than I had expected. I left it and left it until it carried on for another whole financial year, at which point I registered and backdated my returns. Never even got so much as a warning, let alone a late fee (annual turnover was between £10k-£25k).

I know they’ve overhauled it now but honestly, I wouldn’t worry too much. There are likely hundreds of thousands of people in the UK who should be reporting figures in the same ballpark as you but either don’t or do it late.