Well, so far, there has been no direct response from the government. Sadly, therefore, I have little news other than this: http://www.bbc.co.uk/news/uk-politics-22299372
I'm not sure if the costing given here is inclusive of everything the state paid for that day, but judging by the amount of pomp and ceremony surrounding the funeral, I doubt it. Does this costing include the cost of all those soldiers marching in the procession, and standing in the guard of honour, or did that come out of a military budget? Does this costing include the cost of all the gun charges fired in salute, and the soldiers attending the guns, or was that a military budget too? Does this costing include the cost bodyguards and personal protection for Royalty and foreign dignitaries, or did that come out of some other budget? were there hidden costs? Write to David Cameron, and write to your MP, and ask.