Just to add, don't assume that the gliders will always be able to adhere to the left-hand circuit rule. Gliders can get caught out by heavy sink, or be on marginal final glide which doesn't allow them to join the approved circuit.
This time of year that gives the glider a choice between landing in a field full of crop, with probable damage to the aircraft and possible injury to the pilot, or flying a right-hand circuit (or no circuit at all).
You therefore have to assume that gliders may be forced to use any circuit or part thereof, and so need to look out both inside and outside the circuit at all points.
Alarming though this might sound, I know of no collisions between powered a/c and gliders (or between gliders) in the landing phase - there have been collisions near gliding sites, primarily between tugs and gliders, but these seem to occur above circuit height. Having said that, I've seen a number of last minute sightings and consequent manoeuvres, but none which got close enough (in glider pilot terms) to appear dangerous.
The reason for this is, I think, that because there are no definitive rules about where everyone is flying, we all keep a far sharper lookout than in other phases of flight.