"It's what we all do isn't it? I'm doing it and was actually advised by our business manager to come back 4 days before the hols to ensure that the person covering me also gets paid for the hols."
That business manager should be sacked 
This is why people get pissed off and feel (correctly in some instances, such as this one) that they are having the piss taken out of them.
Playing the system to milk as much public money as possible for personal gain and no benefit to the public is appalling.
I am no Novack, I'm the wife, daughter and granddaughter of proud public servants. I support decent pay and conditions for the people who run the country. I have worked as a public and civil servant myself (although not now) and was proud to do so.
But this kind of thing really boils my piss.
Do you think for a minute that a business manager in a private company would give this advice to staff, knowing the company would have to pay for two sets of six week holidays?
You can bet your arse they wouldn't, and they would do their damnedest to make sure the arrangements put in place did not mean they had to pay out from company money for zero company benefit.
But somehow it's fine to do that with public money - because "fuck it, it's just there to be had."
But that money belongs to all of us. Not in a "my taxes pay for this, that, blah, blah" way. But in a "this is a shared resource we all benefit from".
Pulling strokes like this to make sure the highest number of your individual staff are getting paid holiday is not treating our shared resources with anything like the respect they deserve.
It's the same mentality as MPs' expenses. Being able to claim for the costs of setting up a second home near parliament (reasonable) led to a culture of some feeling that it wasn't quite enough to take what was fair if you could switch things around to take more.
Within the letter of the rules, but still practises (getting the mortgage paid on your constituency home where your family was resident and had been before you were an MP) that were clearly dishonest and wasteful of public money.
And then the response was such that now plenty of people think our public representatives shouldn't be paid at all, or have their pensions decimated.
The culture of honest public service is being damaged (both deliberately and through greed and self-interest) and it makes it very hard to argue that the public sector is efficient and worth preserving.