The Skipton/Ilkely corridor is a peculiarity, insomuch as its used by a very high percentage of ABC1 commuters from an attractive, relatively expensive area (where they can afford to live and commute) to Leeds city centre working in a high percentage of financial services and other well paid professional jobs, very much the mirror image of many lines in the south. There's no question that the investment in trains, electrification and resignalling has also helped its case.
I doubt very much if you applied a similar investment to say Middlesbrough - where there are a high percentage of low paid blue collar jobs, where people do not commute as far and generally don't travel much anyway - you are likely to get such good value for money for your investment. Understand, I'm not having a poke at Middlesbrough, but for historical and geographic reasons it has a completely different demographic to say Oxford or even Leeds.
In time, many of these towns and cities will change, especially if the labour market means better paid jobs, which require travel or commuting, start appearing in great numbers. Nottingham, Sheffield, Manchester and Leeds and good examples of up-coming cities. Others are still lagging, but in time, hopefully will recover from their post industrial decline.
Don't forget Leeds has recently had resignalling (controlled from York) and a large expansion in the track layout, because it needed it - and rightly so because its the second busiest commuter town in England very much because of local employment. But frankly, there aren't that many other areas where capacity is all that constrained and some of the load factors on northern lines are quite low - hence the need for subsidy.
As for line reopenings, like the south, there are several possibles, nevertheless they are are quite low BCR ratios. Whereas I'd like to see Woodhead, the peak lines, and various lines in Yorkshire re-opened, the finite pot of railway finances and resources means, again, they are lower priority.
In any case, I'm not sure I agree that things in the north are that bad.
Leeds - most lines in the area power signalled with 3/4 aspect signalling controlled from York. Some lines electrified.
Newcastle - ditto from Tyneside, although there are semaphores down the Durham coast and in Teeside - but it is a terrible pocket of unemployment and low paid jobs. Lines mostly electrified with AC or DC overhead (metro)
Liverpool - ditto, mostly controlled from Sandhills and Warrington. Most lines are electrified with DC or AC Overhead.
Manchester - ditto, controlled from Manchester Picadilly, South and various PSBs in North Manchester.
Sheffield, ditto, controlled from Sheffield. While there is not much electrification in the area at present, this could change in the near future with MML wiring, which would probably include the Doncaster and Leeds lines.
Hull and Middlesbrough seem to be the poor relation, with only recently introduced direct London services and mostly semaphore signalling.
Most lines are similar if not greater line speeds, compared to the south (have you seen the journey times to kent!) and the fares are generally cheaper.
The Transpennie lines have part mechanical signalling, although north transpennine is mostly 3 aspect signalling. But the linespeeds are a mostly fairly respectable, given the curvature and terrain.
But Northerners might be surprised at the pockets of semaphore or very old colour lights in the south!
