I am not sure if it depends upon airline you work for, if it is with BA then LHR is good becuase you have regular flight to DXB on both BA and EK.
Gatwick has daily EK services to DXB
Birmingham also to DXB
Manchester is a second best chance as they codeshare with BA and they have daily flights one in the morining and one late at night on the A330.
Hope this helps
Enjoy DXB