Why all this talk about examiners? There is no test to add a sailplane tow rating to an EASA licence, there's no such thing as a tow rating under the old rules, never mind a test. If there's no test there's no need for examiners. If someone is mentioning examiner to you in regards to tugging they are either:
a) bull$hitting or
b) unwilling to sign your application & blaming "the rules".
There is no requirement to hold a tow rating on an EASA licence to act as a tugpilot until April 2018. Until then you can continue to tow on an EASA or non-EASA licence, you can continue to train people to tow on an EASA or non-EASA licence. An NPPL(SSEA) holder with a DVLA medical can still be a tugpilot & can still train other tugpilots.
When the time comes for you to convert, if you can find a BGA CFI prepared to certify your tugging experience you can get a sailplane tow rating on your EASA licence. If you can find a BGA CFI prepared to certify that you have trained other tugpilots you can get a CRI certificate limited to sailplane tow training attached to your EASA licence.