The transition process hasn't been published yet, so BillieBob and Robin are summarising bits of LASORS
No, we are not - we are quoting European Law. The requirement to hold an EASA licence and the status of national licences is established in the 'Cover Regulation' to EASA Part FCL.
Article 1
This Regulation establishes common technical requirements for:
1. the licensing, training and testing of pilots involved in the operation of aircraft referred to in Article 4(1)(b) and (c) of the Basic Regulation;
2. the certification of personnel responsible for providing flight training or flight simulation training and for assessing a pilot’s skill.
Article 3
Personnel referred to in Article 1 shall be qualified in accordance with the provisions of Annex I to this Regulation, hereon referred to as Part-FCL.
Article 4
1. Any pilot licence, including any associated ratings, certificates, authorisations and/or qualifications issued or recognised by a Member State in accordance with the JAA requirements and procedures before the entry into force of this Regulation, shall be deemed to have been issued in accordance with this Regulation.
2. By 8 April 2012, holders of national pilot licences, including any associated ratings, certificates, authorisations and/or qualifications issued in accordance with ICAO Annex 1, shall have had their national licences converted into pilot licences, ratings or certificates specified in this Regulation by the competent authority of the Member State that issued the national licence.
The (largely pointless) Comment and Response process on Annex I to the Regulation (Part FCL) has now finished and EASA are currently formulating their 'Opinion' to be submitted to the European Commission later this year. It is now too late to propose any changes.
Any UK national (or other ICAO) licences that have not been converted by 8 April 2012 will not be valid for use in EASA aircraft (i.e. those with an EASA C of A). The UK CAA do not see it as their responsibility to keep the industry informed as they did prior to the implementation of JAR-FCL. As Whopity has said, it seems to be that, in their opinion, it is up to individual pilots to make themselves aware of the changing law and how it affects them, the CAA's job is simply to enforce it.