In April, the Standard code introduced major changes in the way in which industries work: see here (http://forum.simutrans.com/index.php?topic=7132.0) for details. Some discussion, I think, is merited of how this ought be implemented in Pak128.Britain, in particular, the requirement to specify absolute numbers of mail and passengers for each industry type rather than the existing "level" system. We also need to consider for which factories to enable this and for which factories to disable this feature, as not all industries should be able to expand on the basis of passenger/mail inputs (primary industries in particular - as Prissi asked, why should a forest grow faster because it gets mail?).
Edit: It will also be necessary to add parameters for factory electricity consumption: a newsagent will use far less electricity (even per unit of production/consumption) than a steel mill. These were previously handled in Experimental by the "electricity proportion" setting, but the new "electricity_amount" setting from Standard means that this needs to be done in Standard, too.