ThomasEdwards...you did not indicate whether you wanted a takedown for compactness when travelling or to be able to switch barrels?

If you just want compactness, you could consider the Holland & Holland system where the barrel and reciever simply comes out of the stock with a quick release mechanism, and there is no penalty in loss of accuracy or point of aim.

Accuracy (and point of aim)in switch-barrel systems will depend on;
1.System used - the integral bolt to barrel locking systems such as used by Blaser/Swissarms etc. are very good in this respect.
2. Quality of fitting the takedown system - and state of wear!
3. Whether the Scope is mounted on the barrel or reciever - mounting on the barrel allows for a dedicated scope for each barrel and avoids the use QD mount sysems - another potential source of innacuracy.