Hi everyone,
I'm new to the forum - I got here via ten-tenths and saw what a good forum this is! What a find all those photos are.
I believe that the number 19 car in question is the 1949 DB2 which was fitted with the 2.6 Lagonda engine (the other DB2s had 2 litre 'Aston' engines), chassis no. LMA 49/3. A DB2 #19 was also entered in 1950, as you have already identified, but looking at some of the pictures I've got, the 1950 is much more like the more 'common' (if such a word can be used for an Aston!) roadcar. There was also a DB1 entered in 1949, but its number was 29!
The car therefore pictured is, I believe, the Johnson/Brackenbury 1949 car which managed just 6 laps before it boiled its water away and, due to the regulations stipulating a minimum of 210 miles between water replenishments, had to be withdrawn. It did make up for that poor performance somewhat at the 1949 Spa 24hrs, however, when it came home 3rd overall and 2nd in class.
As for the other pics, I'm not so sure - I'm better with cars than tracks! I hope that has been helpful.
Right, I'm off to explore the rest of this forum!