I wanted to check a bit about a couple of things including the different types of Audax controls I'm likely to meet having decided to do one or two (or more) events (calendar events, that is) this year.
I guess a standard control will pretty much have one or more volunteers sitting at a table somewhere with a stamp for the brevet card.
Yes.
An info. control, I guess is meant to prove you got to some place by asking you to provide (write on the brevet card?) a piece of information provided at the control point. What do these typically look like? Are they indicated specially on the route sheet?
The routesheet will tell you where the info control is, but not what the question is.
The Brevet card will have the question, usually something like "At this junction, Number of miles to <placename> on signpost", "Name of school on left". You can usually get them without having to stop as long as you can remember them. More bizarre ones include finding numbers written on telephone poles which require stopping and dismounting.
I also gather some controls are actually done by staff at cafes on the route etc. stamping your card, rather than volunteers. Is it normal/expected to buy something at these? (I don't think I'll ever be likely not to do so, at the very least I'd want to top up bottles and maybe scoff some cake/flapjack/sandwich) Is it usually obvious from the route sheet?
Yes, it's polite to support the cafe by buying something, but this could be as little as a Mars bar if you don't want to stop for proper food. For bottle filling, just ask politely. Most places say yes without a problem.
If this kind of control is being used then the routesheet will tell you all you need to know.
Finally, I know that on DIY audaxs (audax? audaxen?, my Latin is nonexistent) you are required to control by picking up all manner of till receipts, ATM receipts or other timestamped materials. Are these type of controls also ever used on calendar events? If so, is it obvious from the route sheet?
Yes. Some calendar events require you to get a receipt from anywhere within a town. The routesheet will usually just provide a list of places in the town that should be open. The receipt should have the placename and date/time written on it, although if everyone submits similar looking receipts (without placenames) then it's not a problem.
For example, The Dean goes through Malmesbury at about 200km. If you're early enough there's a cafe, but it was shut when I got there last year so I went to the Co-Op instead. The routesheet gave all of the possibilities.
For DIY rides you have to pick the controls yourself (in advance), so you need to know that there will be something suitable. ATMs that print the time/date/location are ok, as are most 24 hour petrol station receipts.
Finally, how big is a brevet card? Will it go in standard jersey pockets? Should I bring a ziplock bag to stop it disintegrating etc. etc.?
9cm x 14cm when folded (it's 14cm x 27cm unfolded). You usually get given a Ziploc bag at the start. Don't forget to bring a pen.