Manchester Piccadilly railway station isn't a real branch - in fact it is just an offshoot of the main Manchester branch, it only has cars that are prebooked normally (or at least last time I visited about 4 months ago). Having said that, they did get in touch with you and let you know.

It probably isn't much help now, but MAN airport may have had some automatics - not sure if they would have asked at the airport for you, I'd hope so, but guess we can't be certain. Having said that, MAN airport normally has at least some automatics in stock as most of their prestige cars are automatics - so you could have got a much nicer car if you'd been very insitant on an automatic!

However, I'm not certain if gaurenteed availability applies to a certain type of car? I'm not convinced it is - I thought it was just "We'll give you a car"

PS: In the UK automatics are more rare as we mostly prefer manuals for some reason - it does mean you can have more fun revving the engine....