Hi Andy, nice to hear this. In a few words, you have an economic mountain to climb. Vegatbles are low in value, proportionate to the time needed for growing, packing and selling them. So bedding plants is a good add-on, maybe sweet peas too.. Marketing is not easy at first, until you find customers who like your produce enough to pay a good price, and they need to sense that you are relaible in terms of continuity of supply. You need a reasonably long-term tenancy as the land will benefit from improving with compost.
So good luck, its a great plan, if you can keep another income stream then all the better.