the air-speed velocity of an unladen swallow

...or a piece of string. That is to say: I need a formula for the unformulatable.

Given a warm-ish (please, weather gods) day and the unrestricted supply of alcohol, plus the distraction of some outdoor games and the occasional break for a photograph how much wine and beer can approximately 80 adults consume over a period of two hours?

I could think of this as:

D/12 (2 hours being one twelfth of a day, natch) + A – (G x px) x 80

I mean. I could think of it like that. It was fun to write it down. But it's not going to help me when I'm staring at crates of Peroni in Majestic. Can anyone help?

urgent help needed

OK so it turns out the register office I formerly suggested was 'grotty' now only has two slots available, and even those are squeezing us in. And I checked it on Google Street View and it's not actually that grotty at all - or better than I remember.

I have to let them know today which is better (and neither is ideal):

10.15am, at which we get married in jeans and then go back to the venue and relax and get ready

11.45 am, at which we get married in wedding attire and then go back to the farm and wait for guests to arrive before we do the bit up on the hill

I need to let them know by 4pm. Help! Which is better? J still doesn't care if it's the day before but I do. Will I care if I do it in jeans? Help!