Thanks for the responses.
There may or may not be that much UK data on GBIF from foreign sources. It could be an interesting thing to find out if anyone had time to look.
What might have a more significant impact is iNaturalist https://www.inaturalist.org/ when it used by UK recorders. As a global online recording system, it sends its data to GBIF. But could an agreement be reached between NBNT and iNaturalist that sees data come to the Atlas? Of course this may already be in discussion, in which case great.
Regards,
Tom Hunt - Association of Local Environmental Record Centres, National Coordinator