@Anthanasius: Thanks - it's so long since I used the shadow catcher, I couldn't remember the node setup.
Come to think of it, I can't remember the last time I used AO. Haven't things changed in the last 8 months!
Cool new avatar!

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)