I am not doing my own booze but have experience in events-
I think wine and champagne is easier to calculate as you are looking at 5-6 glasses per bottle, If you were having a champagne reception i would allow 1 and half< 2 glasses per person depending on how long the reception is.
For the meal i would allow half a bottle of wine per person and a half-1 liter bottle of water (unless you having jugs of tap water).
For the toast just need a glass per person or can even do half a glass if funds are tight.
As for the evening reception that is when it gets complicated how long is a piece of string? Are your guests big drinkers?
At a very rough guess most drinkers will probably have 1 drink for every hour they are there however with free bars it does encourage people to drink quicker so maybe even a drink every 30-45mins.
Do you know what the the majority of your guests drink? I'm quite lucky my friends and family are all vodka drinkers so i know i would need plenty of that and maybe only a bottle or 2 of the other spirits nobody really drinks larger so more cider or real ale or guiness.
As for cost again depends on the wine or brands of spirits you choose...Supermarkets seem to have quite good deals these days so you could stock up whenever you see offers, i'm not sure it really saves much these days doing a booze cruise to France.
I think Majestic have a sale or return policy for unopened drinks purchased through them so if you brought through them you might be able to return your left overs for a refund.
like the murphys i'm not bitter
Hitched Awards 2012 Joint Funniest Hitcher (apparently) & Best Flasher