I have 2 Barclays upgrade vouchers and want to use both together on the same booking so that we are seated together. I'm not able to book the inbound flight just yet as it is outside of the 355 days window

I was advised by the executive club to book the outbound first (using 1 voucher), and for the return, I just need to call executive club for them to apply the other voucher and link the bookings together.

This is contrary to what many testimonies... Just wondering if anyone has been successful doing this?