There is a well-established history of artists taking over empty shops for temporary exhibitions or community projects, and in the current economic downturn such activity is being actively supported both by local councils and artist networks.
You should consider agreeing and signing a written contract with the owner of the building in question; and the owner of the building should be made aware of the benefits of doing so.
The 'economic downturn' the UK currently faces provides unprecedented opportunities for artists in terms of spaces to show or create new work, while cutting back on opportunities for funding.