Well the internet has done me proud and I've fixed the AC without resorting to taking the whole car apart. A 1/4" drill bit, a coat hanger and a small rubber grommet and the Beast is back in business. When started poking around with the coat hanger I got over a cup of water drained on the inside and at least that through the overflow proper. It certainly was blocked up and in need of a good rodding. I'll keep an eye on the rubber stopper I've put in place and it was tough to get it in. If it leaks I'll break out some bath sealant for the complete bodge job look.
Had to be at work early this morning to move some databases around. Unbelievably I get time and half off in lieu for this....I can't remember the last time I got something for next to nothing. I'm used to the company taking what it can for nothing. Happy days.