Should Easyjet change their name to Easymoney?

Checked in on time for flight with hubbie and kid, went straight to Security, delayed by megalong queue and staff-shortage, arrived at Gate 10 mins to spare and bumped from flight. Told by staff there £35 EACH to "transfer" to another flight but stonewalled at Sales and charged £297. Later told by others bumped before us from same flight Head Office had approved £35 charge and approached another employee who printed out £292.47 bill and said it would be refunded and £105 charged (would you argue with a steamroller at 7.30am?)

Checked on return, no refund to credit card, no answer from "we will answer your email within 24 hours" helpline, tracked down live person on phone (no mean feat) who said he would effect refund and email me - email says charged £292 and.... no refund.

We did nothing wrong and yet have no recourse to being walked all over by Easyjet. Flight home 30 mins late - they're "sorry" - where's my £292.47? Anyone know what Aviation Authority I can contact??
Additional Details
Sparkey and Offama Trolley - thanks for answers but maybe you should read my small print - I did all the right things - checked in on time and went straight to gate via Security as forced to do - I had no control over any other person's ineptitude. Easyjet said Security delay was not their problem; Security said Easyjet's attitude was not their problem. They work because of and with each other in the same building and there is no attempt at communication between them or interest in the welfare of passengers (who are completely robbed of control) who are paying their salaries for jobs not well done.