If you sow now, there is a danger your plants will be too well-grown and lush to survive a really cold spell in January. Delay sowing and the young plants will be smaller and less vulnerable.
However, it's a good idea to prepare the soil for your row of winter peas or broad beans now, while the wetaher is warmer and the soil still easy to work. Once it's prepared, cover the row with polythene (any old stuff will do). When you roll it back in November or December, the soil will be in perfect condition, instead of a claggy cold mess like the rest of the plot. Planting will be child's play.
If you are on one of the low-lying clayey sites, you'll get better results with winter peas and broad beans if you can raise the soil for better drainage. If you don't have a raised bed, a low ridge will do. The mound where you grew your courgettes, raked over and flattened slightly, is ideal.