I think 1145/46 had what is called a 'forced air' ventilation system, with the fan blowing air into ventilation ducts. The air could possibly have been heated in the winter, but, as JHB says, it wouldn't have been 'air conditioning' as we know it today. As flange lubricator points out they were real 'First Class' vehicles, designed and built for that purpose. In addition to the ventilation system they had fluorescent lighting and seated 42 passengers in individual three-position reclining armchairs.
With respect to the 'First Class' Cravens, there were five - 1147 - 1151. These were converted from 'Standard Class coaches and as a result the seats did not line up correctly with the windows. The history of these coaches is:
1147 - Converted from Standard Class coach 1551 on 27/01/1970. Reverted to Standard Class coach 1551 in June 1973;
1148 - Converted from Standard Class coach 1547 on 16/01/1970. Reverted to Standard Class coach 1547 in December 1974;
1149 - Converted from Standard Class coach 1558 on 01/05/1970. Reverted to Standard Class coach 1558 on 31/12/1984;
1150 - Converted from Standard Class coach 1548 on 02/09/1970. Reverted to Standard Class coach 1548 on 25/10/1984;
1151 - Converted from Standard Class coach 1547 in March 1980. Reverted to Standard Class coach 1547 on 04/03/1985.