If your licence expires prior to 17th September 2012, you may renew it as previously, but its new calendar period will only be valid in full for non-EASA aircraft. The use of the renewed licence for the piloting EASA aircraft will be limited to 7th April 2014 or 2015 as described under the FAQs for UK ATPL/CPL and PPL. Alternatively, you may apply to convert the licence to a JAA licence, which will be valid for 5 years and must then be replaced with an EASA Part-FCL licence.
If your licence expires on or after 17th September 2012, you may renew it as a UK licence and the new licence will be non-expiring. However, when the transition periods end the UK licence will no longer be valid for EASA aircraft. Alternatively, you may apply for an EASA Part-FCL licence and comply with the conversion requirements. See the FAQs for UK ATPL/CPL and PPL.