The Eurostar provides nice connections between Paris/Brussels and London. Does it also provide a good alternative if you need to travel to a more northern destination. To put in other words: if I want to go to Manchester for example, should I also consider the Eurostar as an option?
The Eurostar arrives at London Kings Cross/St. Pancras.
From there you can catch the midland main line (to Sheffield) or the east coast main line (to Newcastle and Edinburgh).
If you wanted to go to Manchester you'd need to take the West coast main line from Euston (a 9 minute tube ride away).
As long as you don't mind changing trains, the Eurostar is a perfectly reasonable way of getting to northern England