Originally Posted by
Tafflyer
Lesson learned here. Always book US-UK Avios trips as either one-way tickets or tickets originating in Europe (cheapest) or UK (possibly subject to APD).
If there is still availability on your LHR-JFK sector then cancel it out of your existing ticket for a refund of the higher charges and rebook with origin UK at a lower cost.
that's an interesting idea. TFC for J/F bookings exJFK would be:
JFK-LHR rtn - $1,290.48
JFK-LHR one way - $506.40
LHR-JFK one way - £371.31 ($501.06)
So booking as two singles saves just under $300.