You can ask, but it may be difficult convincing someone sitting by a window seat to swap with a middle seat. You may have a better chance getting the person sitting in the aisle next to your partner to swap with you. Similary, getting people to swap from world traveller. Whilst it may be possible, you would need probably need to find two solo travellers who would be willing to swap.

Now, the more positive bit. Are you sure the WT+ cabin is sold out? If not, you have two options available to you:-

1. wait till -24hr (on-line check-in opens) try and bag two seats together, by swapping around your seats from the online seal selection

2. pay now to select your seats. Again you can do this via MMB