Thanks guys. I've just issued a fix for that.
I'm no longer chunking the import in batches of 250 so we might see issues with this such as timeouts on larger files and the plan is to re-incorporate the chunking method, but I just wanted to get it working again in the short term.
Thanks for the heads-up.
There is also some strange happenings with date formatting when the exported UKC date contains a '?' for an unknown day/month/year. I'm working on this but just FYI.