The Contessa is a good boat. There is no doubt about that. The only reason I can think of for not buying a Contessa is that, because of their ability as cruising boats, they are sought after and do demand a higher price than many similar boats.
Don't worry about space. I am 6' 2" and 53 years old (so larger girth I would imagine) and can happily live in a 26' boat - as long as the headroom is ok.
Osmosis treatment is another chapter and yes it can be expensive. The question is, do you, or rather the boat, need it? The answer to that will depend upon what you want to do with the boat. If you are interested in cruising with her for the next 20 years then I do not believe that a full osmosis treatment is necessary unless the hull is really far gone and "stogy". Otherwise, treat the blisters as they come along. If you are pedantic, as I tend to be, then go for the full treatment but, a word of warning, the treatment can cost more than the value of the boat in some circumstances. My advice would be to get a surveyor to look at the boat and present a report as to the condition and an estimate of costs to bring her up to scratch.
As far as a boat being a "wet" boat is concerned, I have a theory that wet boats are good sea boats. They are wet because they are not being thrown around, as a result of their weight and hull form, and therefore tend to go more through the waves then hopping over them. This makes a boat wet but comfortable.
Keep us posted as to how things go.
All the best
Aye // Stephen