Most organisers will have a preferred or recommended contractor, details of which will usually be in their Exhibitor Manual. They are usually responsible for building shell scheme stands. Regarding a Space Only site, you are free to appoint your own contractor. Rather than just be guided by cost, think about their overall experience. Do they have operatives in the country or countries you plan to exhibit at? Often they will have a network of operatives that can smooth the passage of your goods as well as build up and break down your stand. They may have freight forwarding or customs clearing agents they know who can add value and avoid any nasty surprises.
ESSA – the Event Supplier and Services Association represents some 200 of Britain’s best exhibition designers, contractors and suppliers of materials and services http://www.aeo.org.uk/
Some simply offer a design and build service; others offer a fully integrated service that can be tailored to your exact requirements. The better the brief you give them, the more fit for purpose your design will be. It is often best to suggest ideas you have rather than to give a completely open brief. It helps to think about what you hope to do on your stand, what you like about other stands you have seen as well as any pet hates. They will incorporate your requirements whilst complying with any Health and Safety requirements to design and build the perfect stand for you. If they are the approved contractors on a particular event they will have some knowledge about other builds and what colours and designs are being used at your event.