JFK-LHR r/t is almost 7k miles distance. Not great for distance based earning programs.
IB just announced changes to their program but they're counting in Euros, not GBP.. 7500 Euros for Oro (OW Sapphire) is definitely reachable if you are paying for JFK-LHR in business a few times per year.
If you want both domestic US lounge access and MCE access, it has to be BA, IB, AY, QR, or JL status.
QR and JL have minimum required flights with them, which is prob not feasible for you.
AY is distance based earning but you'll barely make AY Gold unless you are booking higher biz fare buckets.
BA vs IB -- IB has easier requirements.