April is a good one, or Mayflower. For years I grew St George (guess when that flowers?!) but I think it's discontinued. If so, you might find it in the HDRA seed library.
They're fairly easy to grow (although you do have to net them against pigeons). Just follow the instructions on the packet. I usually plant them where I've grown 2nd early potatoes (leeks follow the earlies); dig it over, lime it, tamp it down well & put the plants in. They are a good crop because they come at a time when there's little else. And they're out of the ground just in time to plant any of the tender summer stuff, like courgettes or sweetcorn.
