Add additional regions to inbuilt region data

[AugustT]

See comment from @AJacksonMCS

"Hi Tom, I think that this would be great to have. If you find a way to do it, may I add a couple of suggestions? -

Include regions for the whole of the British Isles (Jersey, Guernsey, Isle of Man, E, S, W, NI)
Include grid cells that cover the sea as well as the land. I have polygons for all the regional seas if they are of use. I have also built grids (100, 10, 1 km) for the entire area with all cells labelled as per OS standard (i.e. extending further into the sea than the current set of grids provided by OS)."