How tight should my orbits be?
It sounds like "orbit" is UK-speak for making a 360-degree turn for spacing in the pattern.  

I'm not sure what the custom is in the UK but in the US I was taught that you make a Rate One turn (3 degrees per second) for this, giving the tower two minutes between you and the aircraft in front of you (or the one on the ground they're trying to get rid of before you arrive).

The logic is that the maneuver is supposed to create spacing - flying a tighter circle takes less time, and thus creates less space between you and the aircraft in front of you. It also obviously requires more aggressive banking at low altitude compared to the relatively gentle bank required for a standard-rate turn at traffic pattern airspeeds, which as you noted will be easier to control in windy/gusty conditions.