There is one odd-ball to the above explanation, which is G-CPEL. That aircraft only has Club converter seats fitted in the 1st cabin and not in the 2nd cabin, which is why you tend to see that aircraft more on domestic flights than elsewhere.
As a matter of record, the Air Europe 757s (which were 757-236s, same build spec as BA) also had no personal air vents and Air Europe for some reason saw fit to exclude them from all other aircraft (737-*S3s) that it had ordered. If my memory serves me right, the early aircraft ordered for Air 2000 also had a similar quirk, and so I guess it's an Errol Cossey thing to try to save money with Boeing.