Bouquet 'trials' - for Florists

I have visited a few florists and have gotten different answers on this question: Should I be able to see a sample of my bouquet a month or so before the wedding? And how about centerpieces? It's so hard to just imagine what the different color combinations, etc., will look like. I think I would like to see a 'trial run'. Not necessarily completely finished, but just to get the idea. Some florists said they would do that for me. Another said that they could NOT (because they have to order flowers in bulk, unless I wanted to pay for the whole block... )

Thanks for any advice you can offer.