Rudi, thanks to the advice on the board, I've booked and comfirmed the following:

Segment One
Wed UA 907 LHR - EWR 10:00 - 12:55 (3466 miles)
UA 75 EWR - SFO 15:00 - 17:53 (2565)
Thu UA 853 SFO - SIN - NRT 11:15 - 00:25 sat (8451)
Sat UA 2 SIN - HKG 07:40 - 11:20 (1589)

Segment Two
Mon UA 800 HKG - NRT 10:00 - 14:40 (1839)
UA 890 NRT - LAX 15:55 - 08:25 (5454)
UA 904 LAX - JFK - LHR 11:10 - 08:55 Tues (5927)

Totals are - segment 1 16,071 miles
2 13,220 miles

In fact with the current offer for UK MP the segment 1 miles are 17,065 and for 2 14,768 giving a total of 32,373 segment miles. (If only I can find a few more bonuses!)

All segments are confirmed Biz 15G or 15B when its a 747-400. And has anyone noticed that flight 75 from EWR to SFO will become a 3-class 777?

No doubt this is going to be an interesting trip!