Thank you very much for your feedback: this is most helpful. Firstly, I should note that the Standard version of this pakset is currently not being maintained as the last of the maintainers retired
a little while ago. However, I still maintain the Extended (formerly Experimental) version of the pakset, and your feedback is most helpful in that context.
I note that, in the Extended version, the greengrocer is indeed introduced in 1818 rather than 1750; I suspect that the retention of the year 1750 in the Standard version is an oversight.
The historical information and understanding set out is very helpful, I think, and your ideas seem very sensible: I should gladly incorporate them into Pak128.Britain-Ex. I am most grateful for your interest in producing the .dat files and graphics for these additions. For reference, you may wish to note that the work-flow for producing graphics for the pakset has changed somewhat since you last worked on Simutrans: details can be found here
For adding types of goods to Pak128.Britain-Ex (for Extended), you will need to look carefully at the existing pricing systems and set sensible values based on the historical data reproduced in goods.dat for cheese, bread, etc., taking into account the different pricings at different distances. I imagine that spirits would have quite a high value for transport, but quite low quantities, as you suggest.
One small note: I suspect that there may well already be a shop with a yellow and white awning (a grocer, I think, although I have not had time to check) in the pakset, so you might want to consider a different colour scheme for the cheesemonger; alternatively, you might just have the grocer selling cheese in the later years.
Thank you very much for your helpful thoughts and willingness to implement them.