CX 251 and 255 (the two daily night flights) are operated by LHR based crew although on some days they are operated by mix-based. The other three flights are by HKG based crew.

A lot of the outport based crew are really young (even at SP and ISM level) and they are more casual when dealing with pax nonetheless still nice and polite of course. I generally prefer HKG based crew myself as I found them more knowledgeable and professional.

Having said that in my opinion LHR based crew are probably one of the best outport based crew on the CX network. And with CX251/255 arrival time into LHR in the morning (unless you take CX237 on Sun/Mon) it is clearly a preferred choice for many business travellers.

FYI I have a LHR on CX255 myself in Nov in fact