Hi Simon,
Thanks for sharing your story. I could relate completely - my Mum had cancer, twice (Hodgkins lymphoma and then skin cancer) and she never seemed to share anything about her treatment with us. I actually didn't know she had skin cancer until she was away from work...in hospital! What she did make evident was her drinking. I knew she was going through a stressful time, so I let it slide for a little bit, but it all came to a head one day. I actually sought counselling after an argument with her. What worked for me was going to see a psychologist who gave me some techniques to cope with her and to encourage her to seek help. Maybe you can try to go initially, using the links supplied by Jess above. In my situation, telling her to 'get help' was only met with hostility before then.
It does get better too - she has now stopped drinking completely and is leading a much healthier life. I'm really glad I took that step and I encourage you to do the same. All the best.
EDIT: Totally didn't see the "May 2016" bit...where has time gone? Friday brain~ Anyway, I hope my experience is useful still Simon and your wife is leading a healthier life :)