Thanks for the help.Here is my latest thoughts.

GVA-LHR
LHR-DXB
DXB-LHR
LHR-MIA
MIA-SJO
SJO-MIA
MIA-LAX
LAX-JFK
JFK-NRT
NRT-HKG
HKG-LHR
LHR-GVA

The HKG-SIN-LHR is great but I will have to check the schedules.If it adds an extra day to the travelling that might be a challenge fom a work schedule poit of view.CX to SIN I guess then BA form SIN-LHR.

Thanks again