Thanks for the help. I've been working on Plan B for hours:

September MRU - LHR 1 segment in BA First
November LHR - DXB - LHR 2 segments in BA First
Xmas LHR - LAX - JFK - MBJ - JFK 4 segments, one in BA First
February JFK - BGI - JFK 2 segments
Easter JFK - HKG - BKK - NRT - SIN - HKG 5 segments in CX/JL First
May HKG - JNB - MRU 2 segments, one in CX First

With the return flight to London we'll be on 2610 BA tier points so we'll still be set for 2 GUF2500.

As I mentioned I'm not really worried about the reduction in June from 20 to 16 segments for this RTW. I'm sure the partner airlines will be reducing the costs of the tickets by 20% anyway!!!!!ha ha!!!