Smith + Ford + others
Smith use Avia trucks as the base vehicle for their (7.5t-12t) Newton range. Avia used to be related to Korean conglomerate Daewoo, but is now owned by India's Ashok-Leyland group.
Nancy Gioia of Ford recently indicated that, in order to speed up the progress of EV development, she was happy to see Ford's partners sharing their technology with other partners to help increase volumes. So I don't imagine that Ford will be dicating which other base vehicles Smith/SEVUS choose to use. But I guess SEVUS might find it cheaper or more convenient to switch from Avia to some other chassis sometime. Ford already work with Nissan, Nissan work with Renault and just signed a deal to work with Avia. So there is lots of cross-fertilisation going on.
PS: I am interested to know what Smith vehicles you've seen in Leeds.