All you need to do is training as required to pass the SEP proficiency check - you will then have a UK national licence valid on EASA SEP aeroplanes as an LAPL until April 2015 and on non-EASA SEP aircraft as long as the rating is valid.
Requirements for the holder of a UK issued licence including SEP to obtain an NPPL (M) are in para. 4.1.1 of
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