By looking at Equipe GTS calendar along with MGCC Cockshoot Cup (who have both released dates), I've come up with the following so far for MGCC 2018-
07 April, Silverstone National
28/29 April, Brands Hatch Indy
02/03 June, Silverstone GP (MG Live!)
14/15 July, Donington (Incl Equipe GTS 3hr relay)
01 Sep, Oulton Park
I would also expect them to be at Snetterton at the end of September for the BMH 4hr relay, and the fact that the Morgan Challenge is scheduled there on 29th suggests 29/30th. The MSCC are usually an invited grid....