Hi Tom
I've no first hand experience of this particular wiring layout but the compartment under the carpets in the passenger footwell would also be my best guess for the blue 17pin connector location.
Your approach sounds similar to mine - just chip away gleaning info from every source possible then when you feel totally comfortable, get stuck in.
Sound advice from audifan. On my 2001 TDi I think the 80 / 20 rule is appropriate. IE 80% of the time the wiring diagm is spot on for wiring colours and pin locations, and 20% of the time there are minor differences
Cheers Spike