To me, this whole issue will be based on two statements -
"Right of Collective Bargaining and Action’, stipulates: Workers and employers, or their respective organisations, have, in accordance with Community law and national laws and practices, the right to negotiate and conclude collective agreements at the appropriate levels and, in cases of conflicts of interests, to take collective action to defend their interests, including strike action" Article 28 The Charter of Fundamental Rights of the EU.
"For the avoidance of doubt, nothing in the charter creates justifiable rights applicable to the UK except in so far as the UK has provided for such rights in its national law" Tony Blair 2007
This clears it all up?!
House of Lords - European Union - Tenth Report
From 5.29b onwards.