OK great, looks like there's enough interest, and that lunchtimes are probably the best time for most - sorry @RobR, hope you can arrange to come anyway.
I'm going to talk to Keith & find out when there would be a free slot, I'm thinking we set a regular time once a month. Given that it's a lunchtime we'll need to be a bit ruthless about starting on time and setting a time limit for talks, but that can be no bad thing.
How about a 12:30 start, 15m for social, a talk window at 12:45-13:15 which can be flexible, either 1 in depth talk or 2-3 10 minute lightning talks / project presentations. I think 10m lightning talks are a great way to lower the anxiety bar for people who maybe aren't used to doing talks, or where you've got something to talk about but not for 30 minutes. 15m at the end for mop-up, questions, social etc. 15m breathing room at the start/end gives people a bit of flexibility if they have trouble getting away or needing to get back etc (but hope most will make the full hour).
I think recurring themes for shorter talks could be project updates (doesn't always have to be new things, interesting progress updates), development tips & tricks you've discovered, nice tools you've found, anything you'd bring up as interesting / useful / fun around the coffee machine but can flesh out for 10 mins with some pictures or (if you're feeling brave) a live coding demo.
I'm thinking we can create a shared Google doc with all the potential subjects in - things people are willing to talk about and whether that's a 10min or 30min slot, and also things people would like to learn more about, in case that sparks a talk idea in someone else who can then do something on that front.