Another trick to consider if availability is tight is the option of booking into F on one of the legs. This would cost only an additional 25000 miles but may significantly increase the choice of flights available. If you do not actually have those additional 25000 miles do not forget that you can buy them from BA: up to 20000 from one account or up to 20000 per account if you have joined in a household account. 25000 miles would cost £430. Extra miles appear instantly on purchase.

You do have one more Tesco statement date between now and then so of course there are other ways of getting some of those extra miles!