See if SQ UK Res Team can at least help you to verify if refund on SQ side to TA for the tickets in question has happened or not. This could help verify the TA story.

Either it is really stuck at SQ or TA didn't properly apply for the refund yet or TA got the money and is working with it instead of refunding you.

Then you can weigh your options. I hope SQ will be willing to share at least that much and not just deflect you to the TA where you are stuck apparently.