I didn't know that Balea heydeni had become Balea sarsii, but it looks like it is just a name change which is not yet generally adopted in this country, so it should be Ok to continue to use Balea heydeni.

Up to 2005 Balea perversa was the only species recognised in this country. It was then recognised that Balea heydeni was here so in effect B.Perversa was split into two,  but retaining the name B.perversa, now with a different meaning, and introducing a new name for this country of B.heydeni.  This makes older records for B.perversa inaccurate in that they now refer to an aggregate. Recorder 6 should be pointing the older records to the Balea perversa/heydeni aggregate. New records should be input by using the preferred mollusc list which has the split and the aggregate.

As I understand it. it  is B.heydeni which is thought to be the most common species in this country and therefore that most older records probably refer to this rather than to B.perversa under which it was orgiginally recorded, but the only safe thing to do without specimens is to consider them as the aggregate.

The Conchological Society, Journal of Conchology contains a detailed paper explaining the difference between the two species.

Journal of Concholgy Vol 30 Part 2, November 2006, Gittenberger E, Preeece RC & Ripken ThEJ - Balea heydeni - an overlooked but widely distributed Europena species.

Also the AIDGAP key Land Snails in the British Isles (Second edition 2008) covers the two species.

Chris, Mike, thanks very much for all that information. It all makes sense now, and I'm quite happy with the situation as it is.
Regards
Nigel

Thanks for the extra information Martin. I usually take my lead from the UK experts in any particular field (especially the recording scheme organisers) because, at the end of the day, the database is a tool to enable good biodiversity recording, rather than a reflection of varying taxonomic opinions. If someone advises me that UK recorders need the changes to be applied then I can do that but until then I will leave the everything as it is now. :)

Great :)  I will watch out for any changes in the future

Balea sarsii is the name used in the recent Illustrated Guide to the land snails of the British Isles, produced by the Conchological Society in conjunction with the NHM and others.