They were joined by reigning champions of the last three seasons Vauxhall, with Triple 8 Engineering again running a trio of Astra Coupes.
Honda cut its Arena Motorsport-run Civic Type-R campaign down to a single car for the returning Tom Chilton.
Proton completed the line-up of works teams, its two Impians now driven by two newcomers to British motorsport; the experienced South African Shaun Watson-Smith and the young Malaysian Farique Hairuman.
Financial trouble forced MG Rover to pull its works backing from West Surrey Racing's MG ZS assault, but the team cut down from three to two cars and returned as an independent with young gun Colin Turkington and veteran Anthony Reid staying on board.
GA Motorsport (now under the 'Team Sureterm' banner) continued to run a pair of Astra Coupes for the returning Paul Wallace and Renault Clio Cup graduate Charlie Butler-Henderson, while a Super 2000-spec Alfa Romeo 156 was also entered for Carl Breeze.