Thanks for the feedback folks.
Probably jumping was the wrong terminology to use.
What I have sussed today is if you press next to go to the next track, it never "jumps". However if you let the RCD510 change from one track to the next naturally it seems to start playing the new track, then it mutes for a split second and then recommences.
It's quite annoying especially if the track starts loudly. Its obviously not noticeable if the track fades in.
It doesn't seem to do it in "Scan" mode.
I might burn myself some cut down tracks of 15 seconds or so so I can demonstrate it to the garage, but I doubt I'll get anywhere as it seems to be a common feature

Back on to Dynaudio, it must be out of this world. I wouldn't mind hearing one to compare. I'm not doubting that it, but the factory set up is fantastic on its own.
Steven.