The Tridents were used on LHR/NCL and a few other routes including LHR Bilbao which for some reason stayed with NE rather then BA European Division. I think there were a couple of other European routes including Bordeaux and Klagenfurt.
One of the Tridents, AVYD, was written off in a take off accident at Bilbao in 1975.
http://www.aaib.gov.uk/cms_resources...0G-AVYD%20.pdf
The machines flow by BKS/NE were originally built for Channel Airways with an 'imaginative' cabin layout allowing 140 seats. On BK/NE operations they were limited to 110. SFAIK none visited Leeds. Though there is a story of one being shown at a SSAFA display at Church Fenton performing an approach and G/A at Yeadon en-route bak to its base at NCCL.