Green Bird with Red Beak

I have seen a bird of about pigeon size but not as upright which was almost lime green with a reddish beak and had sort of round markings on its wings, It is driving me mad. I have seen it on three seperate occasions now, The first two by the rhynes in Rooksbridge Somerset and the third time in Burnham on Sea. I know what I saw but cant find anything that matches it. Can anybody help me please?