Or try this with cathaypacific.com
HKG-LHR-HKG 11-18 Nov J HK$44K
TPE-HKG-LHR-HKG-TPE same dates J TWD111K which is less than $28K
There's just been a massive argument over at the BA forum
http://www.flyertalk.com/forum/briti...eu-sector.html about a similar issue, except their TPE is a non-UK EU location.