Glad I could help, despard. I don't think 'brill' is terribly modern - and Chambers defines it as 'informal', rather than 'slang'. (PS I'd never use the word myself!)
I think I need to update my vocabulary and dictionaries. My Shorter Oxford English Dictionary shows only: A flat-fish allied to the turbot under "brill".
Too late to do the first and too expensive the second!