Flying a Cat C type aircraft and was wondering is there a standard circling manoeuvre or does each manufacturer have their own version of perfection?
No, each company uses the manufacturer's advice in the manufacturer's training document, then changes it according to the experience (or lack of) of the training department.
I'm referring specifically to circling to the opposite end of the IAP runway. I know the break off is 45 degrees but for how long and is that adjusted for wind?
45 deg off for 45 seconds from wings level ± 1 second/2 knots wind. Previous company never had a time guidance, as most circling was from an off-axis non-precision final approach. Generic advice was to position onto a 1.7 mile abeam downwind (this was ¾ of the first range ring on the lowest scale EFIS map on the 737-300, which is the second lowest scale on the NG) One times drift heading into wind (drift away from runway), three times drift into wind if drift is towards the runway.
Likewise, on the downwind, when timing from abeam the threshold how far do you go in terms of time and how is that corrected for wind?
45 seconds ± 1 second/2knots wind. Previous company was 30 seconds or three times the height AGL in seconds (whichever larger) no wind correction. On the 737 EFIS map, the base of the aircraft triangle ahould be abeam the threshold (useful to know if you forgot to start the clock!)
Cicling can be determined
a) on prescribed tracks
b) without prescribed tracks
-refer to individual airfields to find out.
Some airfields with circling on prescribed tracks may
also allow "normal" circling inside the circling area, if requested. In France, for instance, this is referred to as MVL or MVI (?) circling. If you don't want to use the prescribed track (e.g. to avoid weather) then you request MVL circling from ATC.