Is it possible as a plus member to move my funds over from GIA to ISA? Or do I need to withdraw and buy the shares again? Feel like an idiot for doing that.
Yes. Just start a chat with Support in the app and ask them to do just that
You can transfer funds between GIA and ISA by messaging in-app (regardless of whether you’re a plus member or not).
You cannot transfer shares from GIA to ISA as this is against ISA rules (not just a Freetrade thing).
You need to sell the shares and then purchase them again in the ISA.
You can ask support to transfer the funds to your ISA as opposed to withdrawing to your bank account and then depositing again.
Have fun - went through this and it was truly awful