The simple answer is no.
Unless you’ll pay for it.
Bridal bouquets can cost anything from £40 - £100, and take hours to put together, They use countless amounts of flowers and foliage and take a lot of skill to construct, even if you’re choosing a more simple design.
The time and money that it takes to build your bouquet will cost your florist double if they choose to provide you with a sample bouquet.
However, if you pay for the sample bouquet the florist will do whatever you want as it won’t cost them anything.
I think you would be very lucky to find any suppliers that will give you free samples of items you’re actually going to have for your wedding, with the exception of the stationer who should send you a sample wedding invitation for approval.
Saying that though, if you don’t ask you don’t get. Feel free to ask your florist if he or she will make a sample bouquet (for free), they might even say yes!