Splitting an E-Commerce Site between multiple Users

Hello.

I have recently set up a site with an on-line shop (using the Jigoshop e-commerce plugin). This is working fine, but the client has decided that they now want to split the site over a few different areas that will be controlled by different Users.

I don’t really have any idea how to do this for the best, but my initial thoughts are to have it so that I add a new base level product category (such as London, Birmingham, Manchester, etc) under which all the product sub-categories get created and items posted. How-ever the products are not added under standard categories but (I’m new to WordPress so may be wrong about this) under a custom taxonomy category.

TBH, it ‘may’ be better to somehow split the entire site (including database) for each area so that each can have their own front-page, products, events, or anything else that is added in the future.
It would also be nice if customers ‘could’ have the choice to search all products across all areas if they wanted but this is not necessary.

Any ideas how I can do any of this? I really have no idea where to start and this request has taken this site from something simple I could deal with to something beyond me at the moment.

Cheers in advance.
N