Have just received this reply from the V&A:
"I am writing in answer to your enquiry. Your photos are excellent. Your charger would appear to be possibly late 19th century, or more probably early 20th century. Its style and subject imitates maiolica wares made in Spain and Italy in the 16th century, but the type of glaze, border pattern and palette mean that your dish cannot be early. Following the fashion for collecting the early pottery, many potteries in these countries made reproductions of their earlier wares from the late 19th century onwards. Unfortunately it is not possible for us to pin down the actual pottery that made your charger."
An ID doesn't seem very hopeful then!
Thanks again for your efforts.
Cheers, John.