How about a plant donation day in Caldicot? People can get rid of unneeded plants and help others.
How does a plant donation day sound where people can get rid of any plants they may have in their garden or may have sound advice for gardening. We could help pensioners get the garden they want but require that little bit of help and charity.
HazelClatworthy - Transition Monmouth have regular plant and seed swaps at their events. And Abergavenny Friends of the Earth have a Seedy Sunday in March, doing the same sort of thing. I'm sure they would be willing to help/advise.