Did one almost 10 years ago. "European Impressions". This went for 17 days, and was the sort of tour where they put you up in hotels rather than campsites or dormitories. I was late 20s at the time and figured I could afford the luxury of a real bed every night.

My tour was not full, only about 35 of us on the bus. My age would have been close to the median; the punters ages ranged from 18 right up to 36. I understand that the camping tours attract a younger crowd, and are more geared towards boozing.
The Contiki tour was the second leg of three; I started with a couple of weeks staying with a mate in London, then did the Contiki tour, then I jumped off the bus at the last stop (Brussels) and spent a month wandering across Western Europe with no fixed plan, staying in youth hostels. All three modes of travel have their benefits. I'd suggest that the bus tour is worth doing for its own sake, the experience is worth having. However it is also a good way to get your feet wet prior to a stint of independent travel.
I left my bird at home.

Wandering through Europe by myself did me the world of good... Nevertheless there were several married couples on the tour I did, and even a brother and sister (no, they weren't Tasmanian). So you won't be out of place.