Perhaps the yellow blooming lady's mantle. Although it reseeds you can easily control it by cutting off the spent blossoms. lungwort or pulmonaria might also survive wet winters and dry summers, as well as campanula in the dwarf form. You could try to raise the bed with top soil layered over gravel to grow plants that need better winter drainage such as sea thrift, sedum Angelina, dianthus and any of the dwarf rock garden plants. I think you have a lovely garden to look forward to. Keep growing, Marianne Binetti