England as an entity has no exclusivity of role in Europe separate from that of Britain

It really doesn't get much more bonkers than this ! To suggest that England, a country without a Parliament and few institutions other than the sporting, is somehow separate from Britain is nonsense! Yes of course England has a long history - but its status was long ago subsumed into that of Great Britain. The only way you can define "Englishness" as opposed to "Britishness" is by exclusion. They are the same thing - without the Celtic bits. Ask Englsh people to define what being British means to them and ask a matched sample what being English means and you'll get identical answers. 

England's interests in Europe are identical to Britain's. There is no specific English requirement at all - again except by exclusion of the Celts. Scotland and Wales do have specific needs in addition to the Britsh ones they share with the rest of the UK. England as an entity does not. The English regions and cities certainly do but not as a collective "England". London has nothing in common with the North East, but both have distinctive needs. 

Argue that all parts of the U.K. have special needs peculiar to their Region/area (as well as general British ones) and you would have a good start point for a debate. Argue that England as a collective has needs separate from British ones and you'll be talking poppycock.