Q.Which Variety Of Broad Beans Are Best To Plant In March?
For an allotment in North Kent.

Certified GKH Gardening Expert
Your climate is very different than ours, here, in the US. Most of your area is plenty warm enough for any bean variety during Autumn, but you could definitely choose whatever cultivar of Broad Bean that you want. They are very forgiving of cold temperatures.
Here are some articles that will help:
https://www.gardeningknowhow.com/edible/vegetables/beans/growing-fava-beans.htm
https://www.gardeningknowhow.com/edible/vegetables/beans/growing-beans-in-fall.htm