As a variation on TheMann's intriguing thread on Canada as a major power, what would happen if in the aftermath of WWII the key members of the British Commonwealth(UK, Canada, Australia, New Zealand and...sigh...South Africa) determined to maintain a combined military force, coordinating the design and production of military equipment and offering preferential terms to armaments from one another over all other potential sellers and perhaps even agreeing to a certain combined level of forces.
Obviously substantial reductions will take place in the 1950s but by the 1980s what kind of force level could reasonably expected?