I hadn't given a thought to whether the G1X RAW format would be supported by Lightroom or not, but it turns out not.
I get the following message when trying to import:
"The file is from a camera which is not recognized by the raw format support in Lightroom"
I'm running Lightroom 3.6 with Camera RAW 6.6. Is it just a case of waiting for the next camera raw update?