Most bands are [i]de facto[/i] partnerships, making the members jointly and severally liable for the band's debts etc. It also means you can all be considered to have joint ownership of all the kit you use! However, you can draw up an agreement to make things less onerous on the individual members.
If you are in the Musicians' Union, check their advice on this. If you are not in the MU, it is worth joining for a number of reasons, including £10,000,000 public liability insurance and access to free legal advice.