Seaview Brut update ...
I've had an email from Seaview's Consumer Relations in Australia. They say that on-line suppliers www.everywine.co.uk stock Seaview Brut. I've checked, and they do. They sell it at �46.81 for a case, which is not bad.
Seaview also say that if they were given a bit more information regarding location, they could forward my enquiry to their UK office to try to find a high street retail outlet. So if you did want to specify a location (not too specific - just the county, or a convenient big town), I'll give the details to Seaview. Otherwise, give www.everywine.co.uk a try. They arrange delivery.
Good luck, and happy drinking.