The underground station car parks arn't free and you'll get stuck in jams on
the M40 anyway. Whatever you do either you or your wife are in for a very
expensive and/or long commute. Perhaps it would have been a good idea to check
all this before you came here.

Agreed. A number also drive out to the M40 junction & park there, where the London coaches call. But your coach or drive to outer zones will take the same time as you suggest, and possibly more than 3 hours in total. That's why the vast majority take the train and stomach the price.