Learning Uechi is quite a bit different from learning a grappling art.
With Uechi you can look at the Kata that you know and use that as a benchmark for rank, not so in Judo or BJJ as I understand it.
Each school has it's own system for giving out rank which often includes competition. Traditionally they use a 6 kyu system in Judo so you could move a kyu and not know it if they are using the white-brown-black belt method. I think in Europe they use more belts sometimes.
I wouldn't be hesitant to walk in a Judo school at all. some BJJ takedowns won't score because of rules but groundfighting is groundfighting.
In the BJJ schools I have visited they seem to lack emphasis on the pins which can be important. The flip side is they are better at armbars than I.
So don't think I'm putting them down.
A classmate once had a drunk problem brother acting up at family gathering for example and he had to pin him for several minutes until he calmed down. Obviously choking him out or breaking his arm wouldn't have been a good thing. So those pin skills can be important too.
I wouldn't look to the Kata at a beginner level for any answers.
I will point you to an awesome tape.
http://www.amazon.com/exec/obidos/tg/de ... ce&s=video
There is so much knowledge on this tape it's unbelievable.