Re: It's getting annoying..
In the dojo learn we have the same concept- Yundasha should help beginners to free Sensei to deal with others. In the past, I have had a period in which I had the same problem, my solution was simple - I talked with my Sensei, and explained about my feelings. Turns out, he felt I was interested in teaching, since, siilarly t your own descrition, I used to stop my own training to help others (in our dojo, this is even expected of Yudasha / vetrans).
After our talk, I found I only had to treach at some specific part of the time, which provided me with additional time to train with others. Further, Sensei realized he has to show "favorisem" to those who dedicate time to teach - and invite them to be his Uke and practice with him some. Thus incouraging other Yundasha (we had some) to give more attention to beginners even if their time is limited.
I shoudl also note that in oru dojo too, people first learn Ukemi and only then learn anything else. e.g. first lesson - backwards fall tens of times, then some Korindo Tai-Sabaki, then a single technique involving backwards fall when they are Uke.