Thanks Steve / John ... having looked into it I think I probably waited to seek assistance on how to split them off. Looking at GBIF and a few other sources it looks like they are a bit of a mess and so we probably have to take care. Looking at GBIF records it seems that most of the records around UK shores have been attributed to "pulmo" and so I think what I'll do is treat it like a split and make the existing concept into a sens.lat. called "octopus/pulmo" and then create 2 sens.str. concepts for the current situation.
But I'll see if I can get a proper assessment of whether the current concept can safely be renamed R.octopus
Chris Raper, Manager of the UK Species Inventory, Angela Marmont Centre for UK Biodiversity,
Natural History Museum, Cromwell Road, London, SW7 5BD. (tel: 020 7942 5894)
also Tachinid Recording Scheme (http://tachinidae.org.uk/)