Well they are roe deer and appear to be cast from the same mould.
I doubt that they are very old because roe deer don't seem to have been very popular. They were hunted to virtual extinction during the 18th century, reintroduced in the 19th century and regarded as vermin until 1960. To my way of thinking they were regarded as pot fodder not sporting game, so my guess would be mid to late 20th century. I would also expect a pair to be a buck and a doe. Maybe they were unwanted and thrown away in a sand pit, rather than buried in it. This paragraph is just my thoughts and could be complete tosh.
They are rather nice chaps though.