July is a bit late to plant an African marigold - best planted out in early June. You might get some flowers if the weather holds before the plant gets killed by winter, though, fingers crossed.

As for your front garden, there's a problem - some plants don't mind being in very wet soil all the time, and others don't like it at all, so the trouble is, finding plants that don't mind being waterlogged (probably in winter?) and dryish the rest of the time is next to impossible. Is there any remedial work you can do to prevent waterlogging in winter?

If you can't do anything about the waterlogging, then containers might be the way forward? Does the site dry out completely in summer or does is stay pleasantly moist most of the time?

Look for plants that grow by the banks of streams -
Water Iris, Water Mint etc. Sedge would soak it up, I have plenty of plants if you want some, usually throw them out.