AA usually has pretty good availability out of JFK, to LHR at least. That removes the bulk of the fuel surcharges. Connect on BA out of London to anywhere in europe.
If using the Qantas multi city tool they don’t like routing on AA via JFK for some reason… want to put you via ORD or DFW in coach, or BA services out of JFK with surcharge. Breaking the flight down from origin city to new york (usually la guardia) and then JFK-LHR should do the trick.
You can also use the Alaska Airlines search tool for connections on AA.
IB is another option but it depends on whether they service the particular cities you want to connect. A few years ago we flew MIA - MAD with IB in J and were very pleased with it. The quality of IB's intra-Europe offerings is a whole different story, though.
Try Iberia BOS-MAD or JFK-MAD.
Thanks all, I was a bit hesitant at the Iberia option, but for a saving of $700USD, I think its worth it - especially for a flight I intend to sleep through.

great suggestions!