Your Scotland map shows towns without rail (although some had rail previously, like Callander, Aberfeldy), it prefers insignificant (population-wise) places while ignoring the larger cities next to it (Scone instead of Perth, Bannockburn instead of Stirling, Inverness is missing, Dundee is missing, Aberdeen is missing). All these places are drawn on the map, but not labelled.
All this clearly shows to me how bad it is. Yes it makes it look pretty, but given your task, I would have expected to give you meaningful map labelling.
Something basic like this would get you a long way:
0. cluster population centers into commonly known cities (i.e. show London instead of Islington or Walhamstrow)
1. display names of the top 10 population centers in the UK
2. display towns with stations (if crowded prioritize termination points and junctions, and prioritize larger places over smaller places)
Having said that, its pretty cool to see the new and old network when zoomed in (assuming that it is half-way correct)Compared to AC, 3rd Rail DC is cheaper to install, especially as a retrofit (Overhead wires require bigger tunnels, and increased spacing around tracks for the masts). Downside is that it's not really great for speeds above about 60-70mph, as well as being a bit of a pedestrian hazard. (Ever the one about not peeing on the rails so you don't get shocked? That's 3rd rail DC.)
For the Southern, with it's mostly short routes with many stops, electricfiation was a pretty obvious win, and doing 3rd rail made sense because they could do it quickly and cheaply.
In contrast, the northern routes were electrified muuuch later, after steam had gone away. The main East Coast Mainline from London up to Newscastle and on to Edinburgh wasn't fully electrified until 1991. By the '60s and '70s, with train speeds increasing to 80mph and up, overhead AC was the clear winner.
If you look closely there are a few exceptions - the Merseyrail network in Liverpool is DC. Built 1970s, but using some existing underwater tunnels, and slow speed commuter. Then running ESE from London you have the high speed AC lines leading to the Channel tunnel. Well spotted, the trend generally is quite distinct.