Hello there
I understand your predicament, I applied yesterday for my Mrs FLR and we had the same confusion. I actually ended up asking her to do A2 trinity colleague test even though she had ILETS academic which is a higher level (don't know exactly which level but higher than A2 which is required for first extension). We did the test on Sunday and went to PEO on Monday but presented ILETS (as well as SELT number for Sunday's test which wouldn't have been updated on their system as it takes 48hrs before they confirm the pass mark on the UKVI checking system).
The caseworker relied on the old test certificate even though it is no longer accepted. But as it was the certificate used for her visa application which was approved then the old certificate becomes valid as long as it is at or above the required level.
Please check FLR m specific evidence page on UKBA
https://www.gov.uk/guidance/immigration ... d-evidence paragraph 32D for full details of when an old certificate could be accepted.
Also if you search english language test on this forum you will find earlier discussions covering this topic.
I hope this helps, I would recommend you check again towards your application date as rules may change then
