在英國轉機問題(urgent!!t pls help~~)

Depending on which airlines you are connecting onto... As far as I am aware, you can get check-in all the way to Hong Kong if you are connecting from BMI to Virgin Atlantic or Air New Zealand...
So as long as you are flying on either Virgin Atlantic or Air New Zealand, they can issue your ticket and check your luggage in all the way to Hong Kong at Lyon with BMI...
However, sometimes there could be technical problem on issueing tickets... In which case they will check your luggage all the way to Hong Kong... But only issue your boarding pass to London, in which case you will have to go to Virgin Atlantic or Air New Zealand counter at the flight connection hall to get your ticket issued for that specific flight...
So if you are connecting from BMI to Virgin Atlantic or Air New Zealand, all you require is to follow the sign at London Heathrow saying 'Flight Connection' to the connection hall... After getting through all the security check, you will entry the flight connection hall... Then you can follow the sign saying 'Terminal 3' to catch the bus to Terminal 3 and up to the departure level, as you get into Terminal 3 and before the duty free area... You will see a area full of airlines counter where you can get your boarding pass to Hong Kong issued if they were unable to issue them at Lyon...
In most case, airlines can get your baggage checked in through to Hong Kong, so you shouldnt worry too much... And if it really is necessary to get your luggage at London and to re-check-in... And for BMI flight from Lyon, it depart and arrive at Terminal 4 according to the airport website (www.heathrowairport.com) but the procedure should be the same... As you get into the arrival hall, follow the sign to 'Heathrow Express' to catch the train to 'Terminal 1,2,3' which will be located in the central area... Then just follow the sign to 'Terminal 3'... Heathrow Express is free between Terminal 4 and Terminal 1,2,3
If a re-check-in is required, 4hours should be enough as it would take around 1hour to get your luggage and 30minutes to get from Terminal 4 to Terminal 3 including the waiting time for connection train... Then leaving you 2hours 30minutes to check-in at Heathrow and get through security should just be enough...
So having not have the information of which airlines you are connecting onto, it is hard to say now if you get your luggage checked all the way to Hong Kong... But for sure, if both trip is under 1 ticket, then this will surely not be a problem... But if it is not on the same ticket, I would advice you to talk to the staff at Lyon about the situation and what you should do... But if you are connecting from BMI to Virgin Atlantic or Air New Zealand, it shouldnt be a problem as these airlines are working as partnership...

1) i don't know as i never tried it.
2)I have tried it before. Last time I arrived in terminal 1 and then i went to terminal 3 which took me about 20 minutes.
As u know where is the tube station, it is the same way to go to terminal 3 but just u don't go in the gate for underground.