TomT

You are very close. The only problem is European segments - you have 5:

SEA-IST is actually SEA-LHR-IST which makes 5 European segments:

...LHR-IST-LHR-XXX-LHR-HEL

You need to either get rid of one or buy and extra segment for Europe. Unfortnuately you are already over the 20 segment limit (you have 21 by my count) - so you have to get rid of one. Possibly you can overland (eg train in Europe from LHR to XXX and then fly back to LHR from XXX).