I have a 5 door so I may be talking out of my whatsit, but my wife's previous car was a 3 door Yaris and we were frustrated with the front seats until we sussed it!
I am guessing that access to the rear from the driver's side is difficult, if not impossible, as it probably doesn't slide. If that is right, then hopefully this post will help. I believe that this is common on Japanese cars as a Mitsubishi I test drove was the same.
When getting into the back from the passenger's front door it is important that you do the following:
Tilt the backrest fully forward and then slide the seat forward. To return the seat to the original position, slide the seat backwards until it stops BEFORE you push the backrest up again. Doing that worked on the Yaris and Colt.
If someone can try this and report back it could be useful to other owners. If I am wrong please don't quote this post as I will quickly delete it
