The whole "direct links to London" argument doesn't convince me.
I asked previously for evidence to support the much quoted claim that "this will attract business to invest in the region", based on the number of years that Hull Trains, WMSR and Grand Central had been running. In the end the only example anyone could give was Max who mentioned a call centre that moved from Leeds to Hull (correct me if I am wrong)
If you take the example of Wrexham (which is losing its direct London link) I think it'd be much more important and relevant to have direct links to Manchester and Liverpool. Both are about an hour's drive away but have no direct trains to/from Wrexham (apart from one late night Wrexham - Manchester journey which started recently as a combination of an existing service from Shrewsbury/Wrexham to Chester and an existing Chester - Manchester service).
A direct service to the biggest "city" in the "sphere of influence" would count for a lot more than a direct train to/from London IMHO. A London service may be a nice "day out" once in a while, but a (better) service to a big "local" city might be enough to mean you can get a job there.
Take Barnsley as an example (mentioned by David Dunning). It used to have a London service (a three hour trip in a two-car 170, reversing at Nottingham and stopping at several places) and one train an hour to Leeds (all stops reversing at Castleford). Now Barnsley has no London service, but the Leeds service is now three trains an hour (with one all stops reversing at Castleford, but two are "fast" stopping only at Wakefield Kirkgate). The improved service to Leeds is much more important, and I know of people who use it to commute to Leeds (who'd never have used the hourly stopper before).
Due to the nature of railways there will always be some small places with a direct London train whilst bigger places have none (e.g. Northallerton, Aviemore, but not Bolton or Huddersfield).
However, I think there are some journeys where a London link can be tagged on. For example, with EMT running a number of journeys from Neville Hill in Leeds to Sheffield in the morning (some in service, some light), and back in the evening, there's the scope to stop some of these at Barnsley/Rotherham on the way - marginal cost to the TOC. However, this is no substitute to having a decent service to the cities nearby.