Water Check
No offense, but it may be you that is missing the point. You, presumably, have the option to come back to Hong Kong and collect a full housing allowance, but you choose to live and base in London. (BTW - You could live somewhere less expensive in the UK and commute.) Where can CEPs live except in Hong Kong?
You are a CX pilot and the CEPs are CX pilots. The only differences are the entry mechanism, country of origin, and most likely the amount of experience upon joining. In my post, I wrote that there should be an apprenticeship or period of pay-back for CEPs; after which they should be entitled to the same compensation as expats.