This pricing page makes for interesting reading: http://mail.spamcop.net/pricing.php In a nutshell, it states: "Refunds are cheerfully given upon request if you find that you can't use the system for some reason." I'd say withdrawing the service that's been paid for would be a pretty good reason then, as we won't be able to use the system as intended.
Does this also mean that we lose the greylisting facility as well? I regarded that as a very useful facility and found that it stopped a significant amount of spam. Currently, my account is purely used to forward email on with spam filtering etc. Once the webmail facility is removed, how will it be possible to change the forwarding email address if ever needed?