The best way to do is you simply book the hotel for your friend.
As soon as you arrive, you collect the money in GBP and convert in a bank.
It will be way much easier.
2013-03-19 03:44:36 補充:
What I mean is simple.
1. Book the hotel using your credit card (The hotel does not care who stays there, as soon as the person whose name on the booking shows up.)
2013-03-19 03:44:55 補充:
2. When your friend arrives, you can ask your friend for GBP and you bring those GBP to the bank and convert back to HKD. After getting HKD, you keep the portion you paid.
2013-03-20 03:25:37 補充:
You are making something simple to very complicated.