Rainman, I had great difficulty with 18, which was LOI by a wide margin.
To be honest, I ultimately guessed the solution based on the crossers and then deduced how the "alias" fit in, which had particularly baffled me (kept looking for anagrams of "alias", which seemed plausible from crossers). The UK usage I got last, via process of elimination after the other parts became clear.
I only learned that usage through participating in this forum the past couple of years!
I've been solving cryptics for well over 20 years and have gradually built up a decent toolkit of UK-based terms, though rhyming slang remains a formidable obstacle.