It looks like this was released in the USA and Canada before the UK, because it was reviewed in Cashbox dated 23rd August 1980, in Record World dated 30th August, and the US Copyright Office has the publication date of 11th August. US and Canadian copies at Discogs show (P) 1980 on the labels. I didn't think the US Copyright Office would normally register a copyright that's held in another country (by EMI Records Limited in the UK in this case), but if the US was the country of first publication, that would explain it. Presumably this UK copy has an 8101 date code on the back cover?
Proof here we cannot rely entirely on all catalogue listings. My Music Master 1996 (two volume) dates this as Sept 1980, yet sleeve and labels are P 1981.