Update.
After I emailed SPOT and asking why they don't have a method to cancel subscription renewal online, I was told I have to call then on an international number.
I did some research into consumer law, both UK and EU, and basically if a company sells a service 'at a distance' either by phone or online, they must provide a 'form' to cancel said service. I cited some text from the legal stuff I found in a reply to them, some from Which?, some from Citizens Advice Bureau and some from an EU Law article.
SPOT promptly cancelled my automated renewal, by email.
We are sorry to hear that you wish to deactivate your SPOT service. It has been a pleasure to serve you as a SPOT customer. We want you to know that we truly value your business.
As requested your SPOT service will be deactivated on [date] a day before the next renewal, however, we would like to extend to you a generous offer. We would like to apply a $60.00 customer loyalty credit to your account for your annual renewal to contiune to enjoy the same benefits and features at a discounted price.
This offer is only available 5 days from this email, and if you decide to re-activate your SPOT service at a later date, will not be applicable.
So they are also trying to bribe me to stay. No thanks.