mines the other way around, ctek is wired in to the starter battery - i guess when that's topped up it'll switch over to charge the leisure just like it does when driving.
I have a basic non intelligent charger. I attach the hook up cable to the bus, plug in the charger inside the bus then plug the charger output to the Hela accessory socket (like a cig lighter) on the dash. I've done it like this for 20 years though I can see why it might not always be a good idea for some. I suppose it might blow the clock or the radio for example if you got a voltage spike.
As the VSR will sense in either direction, doesn't really matter which battery the charger's connected to.
I don't think my VSR will trip unless it gets a signal from the alternator and voltage regulator though. Does the CTEK take care of that?
Have you just got a relay operated off the alternator? A VSR just senses the battery voltage(s) and switches accordingly. Bit of a wobble when it joins both batteries together, but a brainy charger like a CTEK is keeping an eye on this, so usually no prob.