If you are doing T4 Europe to T1 you go through the T1/T2 FCC not T4
You're right, I've turned things around

Thanks again!
Actually - does that mean that you can take the air-side bus from T4 to T1 (without being baggage checked), and then i.s.o. going to the T1/2 FCC just exit through immigration there? (And then re-entering via Zone R again.) That would in general be much quicker than taking the HEX. Unless there is a queue for the bus of course.