I was impressed with the range of flavours in Holland for Gouda which I haven't seen available elsewhere. I guess they feel there isn't an overseas market for the stranger ones. I recall a cummin flavoured Gouda which was something I still yearn for.
Easy enough to get in London.
My local cheese shop usually has it in stock:
http://www.lafromagerie.co.uk/cheese...origin=holland
Whole Foods Kensington has a decent selection of Gouda. It's around and there are plenty of places that sell it online in the UK.