Yes, I'm sure the echo is annoying - what I meant with 'not noticeable' was the situation if you mute the speakers on the TV, and only listen to the external speakers.
Don't bother with the AV3 trick... it would be technically OK, but won't change the delay issue at all. In addition, the TV would get only composite video from the DVD instead of RGB through the SCART, and the picture quality would suffer a lot.
I'm not too familiar with the details of BV8, but from a quick glance it seems to have Powerlink outputs for external speakers. You could easily connect your Pioneer to those. As a nice side effect the volume of the external speakers would change along with the TV, and you could listen to program from the TV's tuner as well.
However, I'm not 100% positive that would fix the delay issue. Hopefully someone else (with Beolabs connected to an 8-32) can confirm it before you go and purchase the adapter cables!