I was once told that a rule of thumb is 'the drier the drink, the less
calories'.  Which rule of thumb I ignore, seeing as how I'd rather
have a little less of  what I like (red wine) than more of what I
don't (dry white).  I have marked a wine glass with 125 ml and 175 ml
lines, so I can keep an eye on how much I am really drinking.

Anyway you can get a list of actual cals in drinks here
http://www.caloriesperhour.com/index.html

Or get yourself a calorie book.  I think you're in the UK like me, in
which case try the Calorie, Carb & Fat Bible - costs about 12 quid in
Waterstones and for me, was 12 quid well spent.  You can often also
pick up smaller (less comprehensive) calorie books free with slimming
magazines.  

C