I would say that it's usually good practice to do a small dog-leg and position yourself behind the downwind aircraft, even if they haven't called downwind yet.
The Standard Overhead Join poster from the CAA website:
http://www.caa.co.uk/docs/33/ga_srgw...osterJan09.pdf
Last edited by SirLaughalot; 9th August 2009 at 15:52.
Reason: Additional information