Forgive me for being impertinent, but is the amount owed worth the hassle all told ? I'm assuming it is
See above JR482, last bit of the quote
I have travelled in the last 2 years, but way down on before. I have also had to get back money paid to airlines. One completely ignored all requests for a refund, the other gave me charming diversionary offerings despite taking my bank details several times to 'refund' the money to my bank. I gained satisfaction after a year (due to optimistically waiting) through the credit card company.
For lesser amounts, which of course depends on one's circumstances, there is a point where the effort to reclaim what is rightfully yours outweighs the amount. By rights there should be a ring-fenced/escrowesque fund within each airline to protect customer's money when services offered and paid for do not materialise.