Some councils try to insist on liability insurance if you erect a stall (mine, Cambridge, currently doesn't). Some councils say you need a permit to collect money, but unless there's a special local byelaw where you are, I don't believe you ever need a permit to campaign on the public highway.
Here's what I wrote on this subject for the forthcoming revision of the NO2ID Campaigner's handbook - if anyone has any suggested revisions to this general advice, please let me know.
1.4 Your right to campaign
Many people campaigning for NO2ID have never been involved in any sort of campaign before. You may be one of them. Perhaps the greatest strength of our campaign is the broad variety of people who have never before thought of themselves as "political", but are so outraged by the government's ID card and Identity Register plans that they have decided to take action to oppose them. However, if you've never done anything like this before, you may initially be unsure exactly what you are legally allowed to do, and what other people will find acceptable. It is perhaps ironic that those of us who oppose the Home Secretary's plans to invade everyone's privacy must go out and impress our point of view on others.
Everyone is entitled to campaign. It is highly unlikely that you will ever be stopped or asked what you are doing while you are campaigning on the street. You do not have to notify the police beforehand unless you want to campaign within a kilometre of Parliament (Serious Organised Crime and Police Act).
You are entitled to have a stall, display posters and distribute leaflets on the public highway. Some councils have byelaws that prevent you collecting money without permission.
You should not obstruct the highway as it is an offence “to cause a wilful obstruction of the highway without lawful authority or excuse” (s.137 Highways Act 1980). However, a stall that doesn't obstruct the highway (or pavement) should not cause a problem. A few councils say that anyone erecting a stall on the public highway must have third-party liability insurance. Unfortunately NO2ID as an organisation does not have such insurance.
If you're on private land (such as a supermarket or station forecourt), you will need the land-owner's permission to set up a stall or distribute leaflets. Permanently attaching posters to someone else's property without their permission ("fly-posting") is an offence.
It's worth stressing once again that campaigners distributing NO2ID leaflets on the street or setting up a stall on the public highway are highly unlikely to have any problems of any kind with officialdom. If you should be approached by anyone who seems official and who objects to what you're doing, be polite, and find out exactly who they represent and what they object to. If you're on private land, the owners are within their rights to ask you to leave — find out where that property ends, and move off it promptly and politely. If you're on the public highway and the person you're speaking to isn't a policeman, your best course of action may be to summon the police to adjudicate, since they will usually have a much clearer idea of what is and isn't permitted (and why) than council "wardens", community support officers or similar.
Above all, remain calm and be polite.