It depends if you want to set yourselves up as a formal club with memberships and a committee, and so on. If it's just informal, with no membership fees other than a "donation" to cover the cost of the hall and the teas and coffees, I don't think you need to do anything. You might want to consider public liability insurance (in case a knitting fight starts up)! - but otherwise, I'd ask the people who run your village hall, what other groups are there, so you could ask them how they set up. Open a building society account so you can put the money in there, and pay the hall when they request it.