A close relative of mine works for the CPS. It would apparently be unusual for a case to be introduced to them from a lay person. He suggested that if you have documentary evidence, you take it to the police, but presumed that the "VAT man" would be investigating after (as you claim) some anomolies had already been detected by him.
Surely if Customs and Exise had found that fraudulent claims had been paid out, they would carry out their own investigations, both internally (to find why they were incorrectly paid out) and into Unique Air and its directors?
I cannot understand why you would think the CPS would need pushing on this? Had the relevant authorities found what you say they found, then a case would be brought by them without interference from ex employees. If that were the case then I wonder why those ex employees, who worked in the office (myself included, albeit occasionally) have not been interviewed both as witnesses and potential suspects.
I like the theory though.