You have full control over your Domain Name ownership, but some restrictions apply that might hinder your Renewal process.
For .UK Domain Names, please take note that you can only Renew its Registration (3) three months from the Renewal Date. As such, renewals done earlier than the said period cannot be processed.
When it comes to the Domain's expiry, our system proceeds to Auto Renewal as scheduled. If all of the attempts fail and you do not Manually Renew your Domain by the expiration date, it will go into the Renewal Grace Period — which lasts for 30 days. By the end of the given Grace Period, your Domain that hasn't been Renewed will be Deleted.
Hence, we strongly suggest renewing your Domain for the longest term, or setting up the Auto Renewal option for security and ownership purposes.