I grow them every year and sow in October, just as a no-faff option. Bung them in and walk away, putting a few extra seeds in to allow for losses. You an always pull out any overcrowded ones once they germinate. I've tried and failed to overwinter normal broad beans, but these are tough and hardy critters that shrug off anything the weather throws at them and just keep going. I know Sunshineband starts hers in the greenhouse in early spring and plants out. We both get crops, so take your pick on sowing time
They are very productive and make bushy plants of several stems each. The pods grow in clusters of 3 or 4 and although they are small with only 3 or 4 beans in each, there are masses of them. For the space, it is a bigger heap of beans overall than a normal broad bean crop
Large pea sized as Florian says, they are very tender. If you let them get large, they do have thicker skins, so try a few early and keep on trying, to see where your own cut off point is. Or leave any bigger pods you miss for your seed crop next year, then it is a free heap of beans and you can be extra smug