you can sow loads of stuff now - my favourites are dwarf French beans (not climbing or they won't have time to reach maturity); borlotti beans; mangetout peas; early peas (eg Meteor or Douce de Provence); lettuces; all the salad stuff eg radishes, corn salad, pak choi, Chinese cabbage; also broccoli raab which grows really really quickly and is like calabrese. Also early carrots (Nantes or Paris Market varieties). And chard/spinach/beetroot.
but make sure you sow into damp soil as it's easy to let the seeds dry out this time of year. And even better sow into modules in a cold frame or similar as I find seeds get eaten by the slimy ones as soon as it rains...