any recent traveller on ADO or Cristobal Colon bus lines able to give me an idea of 1 way cost please? Any other comments?

I just took this trip in July with my family. We took the Uno. The price was 435 pesos. The ADO is 314 pesos. It was a very comfortable trip. There are discounts for seniors. You can check everything out at this website.
http://www.adogl.com.mx

Go to "uno.com.mx" it will give you their prices and also link to "ticketbus" which will give you the prices for other lines to Oaxaca. Uno is the nicest. It is a level above first class. The other lines are fine though. Tee trip is about six hours if you go first class and they are taking the toll road.

If you go to the ticketbus.com address, they do have an english option which might be helpful. Also, you can make seat reservations on the site which will be held up until 2 hours before departure.

we went from Mexico, DF to Oaxaca, one-way on ADO about 2 weeks ago. It cost 283 pesos. Remember to bring lots of cash, because the bus company doesn't take credit cards.