Inter-town buses around here are operated by First, with seats marked off like this:
http://www.passengertransport.co.uk/wp-content/uploads/socialdistance-640.jpg
To the best of my knowledge, Ipswich Buses (which runs services within the town) hasn't taped off seats but drivers are only allowing reduced numbers of passengers on each bus.
Greater Anglia trains have some seats taped off around 'peak flow areas' (such as near doorways) but not throughout the whole lengths of carriages. However passenger volumes are currently so low (often with only one or two passengers in each coach) that it's not necessary anyway.
While the London Underground has lots of signage encouraging social distancing (and, for example, floor markings at stations), seats aren't taped off on board trains.