If you have 700k avios, you could consider buying some J flights on BA.com (BA metal or AA if flying TATL to Lon direct) and vastly reducing the the price using Avios. It's not a great redemption of points per avios, but you could quickly get to BA Silver (Sapphire) that way. You'll also earn back avios at the same time. I'm certainly not a pro on this, but if you're a single traveller with that many points then attaining OWS should be straight forward.
I am in BAEC and my first flights of collection year were LAX-HKG-BLR and back. I flew in PE on CX and gained 340 tier points, more than half way to OWS. If I had credited the same flights to Marco Polo, I'd have barely made it a quarter of the way there.
Best of luck
