Transferring third-level domain names with the co.uk or org.uk extensions is a lot different when compared to the standard transfer procedure. While there are similarities regarding the domain's status and the ID protection - this transfer is characterized by the fact that there is no EPP key requirement, and the REMOTE registrar/hosting provider has to start the transfer process. The third-party Registrar requires one additional string combination, also referred to as the IPS-TAG. It is absolutely the same for ALL the .uk based domain names for our Registrar:
PDR-IN
You need to provide your current Registrar with this tag so that they may start the migration process on their side.
Another thing you should keep in mind about these TLDs is that the transfer process DOES NOT renew the domain for one year, which is quite a distinctive difference. The good news about this type of transfer is that it happens immediately. When the remote Registrar enters the IPS-TAG, the domain will be instantly moved and will not abide by the standard 14 days rule.