Thanks for the advice Jim!
I've already raised a complaint for them being uncontactable and the situation I was in earlier. I cancelled the auto-renew policy through their portal plus made sure the agent on the phone confirmed that the auto-renew was cancelled so I won't be giving them any more money (thank god). I might sell my bike within the 6 weeks though to buy myself a BMW F800 ST for a European tour I'm planning so I don't think I'll get the dummy quote just yet.
I'll wait for them to make the next move on this as they said they would contact me to confirm the cancellation so I think this might just be a case of the first-level customer support employee being clueless (both on Europa Bike and the under-writer side) so hopefully they get their act together and apologise instead of cancelling but we'll see.
I'll let you know what happens and thank god for this forum post otherwise I would have been truly stuck!
Edit: forgot to mention that I tried making the change in their portal but just get a generic error which seems to be their website's main response to any action