[Rich in Vancouver]

I would say that the A/C system loss is minimal each year. I do my own top-ups and have found when I hook up the pressure guage on my refill kit (Not sure if they are available in the UK) that there is literally no change year to year. I bought a new refill gas cylinder 3 years ago and haven't had the need to use it yet on either my ZT or MGF.
As for the drains, I believe that one of them was deleted as part of Project Drive but you should still find one in the plenum. I should think it would be easy enough to just knock out the plug and put a replacement drain tube in.