I suspect the closures might come under the Thatcher government; in OTL, the
Serpell report advocated an even more brutal hacking of the railway system than Beeching did in OTL; fortunately, the Thatcher government backed away from the ideas. ITTL, Thatcher may be more receptive to the idea of shutting uneconomical branch lines.
As regards B.R, there'll be some significant differences. It's unlikely that it'll be able to afford the electrification of the ECML, or the WCML north of Preston. We're unlikely to see the development of the
HST, APT, or the Freightliner network, things that in OTL preserved BR from utter destruction and paved the way for the spectacular rail revival that began in the late 1980s and continues even today, despite the recession.
Steam traction will probably continue until the 1990s, that is unless, as I stated above, Thatcher gets involved, and coal is in distinctly short supply. Elements of the BR Modernisation plan that were in OTL quickly ditched despite no real problems, such as the
Class 14,
Class 35, and
diesel railbus, will ITTL continue to be used on the BR network.
For around 25 years, this network will be hugely expensive and a weight around the neck of the British economy. However, if it is able to survive intact until about 1990, the benefits will be significant, as rail travel really begins to take off. If a Labour government is in power during the 1990s, then BR has the potential to become the envy of the world, with a vast, interlinked, thriving network. Even if the Conservatives are in power, the system's ever diminishing losses, and rising growth, may attract investment, and the delayed introduction of something resembling HST.