Jeroen C, the overhead join is intended to allow positive identification of the active runway and a descent to circuit height on the dead (inactive) side of the airfield. You arrive overhead, usually 1000 feet above circuit height, and descend in a turn (all turns in circuit direction) so as to cross the upwind threshold at circuit height, joining the pattern crosswind. The system has its critics, but I think it works well. The main possibility for conflict occurs if two aircraft arrive in the overhead together, and another point for exceptionally careful lookout is as you turn downwind, as aircraft already in the circuit may be coming from a wider crosswind position.
As for the RT, maybe "G-ME [position] request G-THEM confirms visual"? Although there are standard calls for standard scenarios the RT manual is not an inflexible script.
Last edited by FNG; 30th May 2004 at 09:39.