Someone's already done the UK as an OpenTTD map: https://wiki.openttd.org/en/Community/Scenarios/United%20Kingdom https://wiki.openttd.org/en/Community/Scenario

Someone's already done the UK as an OpenTTD map: https://wiki.openttd.org/en/Community/Scenarios/United%20Kingdom https://wiki.openttd.org/en/Community/Scenarios/United%20Kin... , although I suspect that one cell =~ 100m makes it hard to accurately represent the real train density.