I couldn't find it in the cancelation guide so I assumed it was before the billing date or is this wrong?
Also it's probably a stupid question but does it start renewing the subscription for a month by month at the £17.58 price or does it start another year long contract?
The price gets revised at the end of the year from 13th renewal onwards. This has been the trend as of now.
You can cancel it on the 12 th month to stop renewal.