Even as late as the Labour-SDP split, you still had a couple of constituencies with detached enclaves. Wiki suggests Stirling and Falkirk was the last one, but from a brief consultation of "Boundaries of Parliamentary Constituencies 1885-1972", you can add Clackmannan, Monmouth and East Flint.
Bath had a small detached portion between 1997 and 2010 - the parish of Freshford formed a detached portion of the Freshford ward of the then Wansdyke council which was added to the Bath constituency.
https://boundarycommissionforengland.independent.gov.uk/wp-content/uploads/2015/03/5th-Periodical-Report-Vol-4.pdf
