I've done it for over a year now, and use VitalTax, which was free for first year, and now costs something like £10/submission
https://vitaltax.uk/
Whatever spreadsheet you use to track purchases/sales, just link to the relevant cells in that - in the 'template' (VitalTax add-in, in Excel)
So - just add a vitaltax sheet in your workbook and then link back to the other sheet.
It works well, is accredited of course - and is a LOT less than most things like SAGE etc
[pretty sure it was a thread on here that directed me to VitalTax. have a search]