Bite the bullet time for Brons
If Mr Brons agrees with his PA and Constituency Office Manager, Mr Beverley's condemnation of the BNP then, as a BNP MEP, it is his duty to resign from the party, thereby setting a good example for the remaining decent members of the party to follow.
If, on the other hand, Mr Brons wishes to remain a member of the BNP (and get his money's worth from his Life membership), then presumably he disagrees with Mr Beverley's defamation of the party. If he disagrees with Mr Beverley then he should say so publicly and give his reasons.
Regardless of whether Mr Brons agrees or disagrees with the substance of Mr Beverley's censure of the BNP, if he takes no action against Mr Beverley, then he lays himself open to the suspicion of conniving at his public attack on the party. He puts himself in a false position and appears to be a hypocrite.
Turning to Mr Beverley, one would put the following questions to him. If the BNP is as bad as you say, then what are you doing working full time supporting Mr Brons, the BNP's senior MEP? Does your right hand know what your left hand is doing? Does the money you receive for supposedly helping Mr Brons to perform his duties as an MEP outweigh your antipathy to the BNP? Should you not consider your own position and resign, before you compel Mr Brons to dismiss you?