Just about anything you wish should grow in Sutton, nice, warm Surrey, but I would start with my Spring bulbs, Darwinian Tulips, the fancy ones need renewing, and then daffodils and various narcissi, so they come up early between things which will flower later. I googled 'Flowering perennials UK' to see what came up, there are some nice, reasonably priced collections, and a lot of individual suggestions, but really it is down to what you like. For example the missus likes salvias, I prefer geraniums, another approach is to visit a few gardens, Wisley is not too far, but I am sure there are others in your area.