Do you really want to start a club?
This is a very formal arrangment which takes work, meetings, arguements, insurance, bank account, Secretary, Treasurer, Commodore, AGM etc, etc, ::)
A comitee to argue about rules, dummies spat our of prams, teddies at 10 paces etc, etc,
And it you ever want to wind it up.................... :'(
You will need insurance as has been pointed out.
What other formalities you need to go into I do not know. But I am sure somebody on here can tell you.
There are many informal groups, some that have websites. They even have names.
It is just like minded people who meet regularly at a spot on some water.
This would be an easier way to go.
How do you start an informal group?
Just go regularly yourself. If somebody shows an interest, ask them if they want a go with your boat. You might get a few people started off.
Advertise on here perhaps.
Check to see if there are any other RC clubs/groups in your area, perhaps for aircraft or buggies. Let them know what you do.
You could also try looking at the Clubs List
http://www.modelboatmayhem.co.uk/forum/index.php?board=112.0 and asking them what the suggest. If they are posting on here you culd PM them. Others list a phone number.