The worst way for the world to end is global thermonuclear war ... because of the after effects, particularly the radiation, obviously. A large asteroid strike is nearly as bad. The third worst way, surprisingly, is the impact of a large solar Coronal Mass Ejection. This would wipe out the power grid, including the transformers; in the absence of any kind of power the transformers themselves could not be fixed so everything depending on electricity would crash - including the economy.
The problem is that our current population in England of around 53 million is sustained by our
Domesday book period (around one million). If agriculture fails, however, we revert to hunter-gatherer status .. just ten thousands individuals in a country the size of England!
In the catastrophes above, trashing the infrastructure largely leaves the population intact. They fight viciously and starve over the next months, consuming much needed resources and wasting the period of grace before many supplies become unusable. This is why the 'best apocalypse' is more like a souped-up version of Ebola or The Black Death: a pandemic which is aggressively virulent, has a long incubation period (for maximum infectivity) and near 100% subsequent mortality. Yes, our civilization will crash, but the infrastructure will not be too damaged in the process.
And then you'll need Lewis Dartnell's book "The Knowledge: How to Rebuild our World from Scratch" from which the apocalypse palette above was taken.
Dartnell, a prolific science writer, organises his recovery material under the major themes of mediaeval sustenance: agriculture, food and clothing, materials (clay, lime, acids, nitrates, metal-working), medicine, power, transport and communications. There's not enough detail for anyone to actually construct (for example) a working plough - but at least we townies are told how it actually works, and what its function is - and that it therefore has to be on the list.
Well-written and full of interesting little snippets as this book is, reading it is to be reminded anew how precarious our comfortable lives actually are. If the ATMs stopped and the supermarkets failed, how scarily different things would be, and how quickly!