Originally Posted by Guy Betsy
CX's lounge in London is nothing much to boot. Better for you to stay at T1. But if you are just connecting, are you allowed to the Arrivals lounge? Of course you do have to clear immigration and customs and all that. If you are taking CX, then you'd have to eventually make it to T3. But if you're taking BA, then just stay where you are. Again, BA's F lounges in T1/4 are much better than CX's lounge in London.
OK, here's the thing about LHR transit. If you want to access the BA Arrivals Lounge, you will need to clear customs & immigration and exit to the "landside" portion of the terminal. If you arrive on BA in J or F (which I assume since that's the only way to get in the Arrivals lounge), then you should get a "fast track" card to expedite you through passport control. Then you can use the BA Arrivals lounge, where you can shower and get a hot breakfast. Afterward, you'll have to head over to T3 for the CX flight. I know you can walk, it's about 10-15 minutes, there might be a bus too. You then have to re-clear security to enter T3, but there is a Fast Trak for premium passengers.
The alternative is -- upon arriving at LHR, proceed to the Flight Connections Center, where you will clear security again and take a bus directly to T3. No passport control, although lines at the FCC can be really really bad, and I believe FastTrak there is only for OUTBOUND BA passengers. Also, sometimes you have to wait a while for the bus. It could very well be faster to do the landside transfer, and since that's the better lounge option, I would probably reccomend that route anyway.
At T3 you can use the CX lounge, which has a separate F section with a slightly more robust food & drink offering than the J section. It's certainly a nice lounge (and I love the dim sum), but nothing that special, and definitely nothing close to the HKG lounges.