Having never tasted plover, it's hard for me to suggest an alternative but possible substitutes which you might come across are pigeon, quail and guinea fowl. (Pigeon is cheap and often available from traditional butchers - but it can be full of lead shot. Intensively reared quail are very small but very tasty; they're available from butchers or some supermarkets. Intensively-reared guinea fowl can be found in larger branches of Tesco, as well in butchers). Butcher's market stalls often seem to have game birds.