Originally Posted by
Stampe 
Unfortunately current CAA/NATS policy is only to to give that tolerance to verified squawks.Those wearing conspicuity squawks do not get the tolerance.
Got a link or reference to this policy? I’ve been out of the NATS game for a short while but the +/-200’ was permitted for all aircraft.
Back in my day verified mode C could only be associated with a validated mode A target. A target on a conspicuity code was not considered to be validated even if identified by some non-secondary means, hence unknown traffic or that on a conspicuity squawk had to be avoided by 3000ft or 5000ft (depending on circumstances).
As for the +/-200ft thing, that only applied to assigned levels (and consequently only to identified targets).
I know things have changed but I thought some of these basic principles still applied; with some, at least, in SERA. Or meringue?