My suggestion would be to approach web sites that florists go to, there you'll tap into the biggest audience. Maybe try and find one that sends out newsletters.
If you google for - lists of uk florists - that will get you started.
If you try and set up a website to do that, you'll spend a fair bit of time even finding a way of persuading florists to even find your site.
As another approach, find a florists magazine and get them to do an article about you and what you have to offer. In this case google for - floristry trade magazines - or similar.