How easily does the Eurostar to London connect with trains to Northern England?

The Eurostar goes to St. Pancras International station in London.

The Virgin Trains Pendolino service has a train to Manchester every 20 minutes, and takes about two hours. This leaves from Euston station, which is about ten minutes walk from St. Pancras. The public transport connections between the two stations are not very good, so I would generally walk; if you have a lot of luggage, or otherwise struggle to walk, then I would suggest a taxi; by the time you've walked to the platform for the underground and back up again in Euston, you might as well have walked from station to station.

I would recommend leaving St. Pancras via the Midland Road exit - it's signposted "Exit (Midland Road)" from inside the station, or also signposted "Taxi". There is a pedestrian crossing directly in front of the exit; cross there and then turn right. Walk alongside the Francis Crick Institute (currently a building site) and turn left when you get to the next road (Brill Place). You can walk straight along this road until you reach the side of Euston Station. There are two or three locations where the road is blocked for cars, but pedestrians and cyclists can walk straight along here. When you get to Euston (it's a large, ugly building that directly obstructs your way), cross at the zebra crossing and then turn left on Eversholt Street. After a minute or two, you will find a set of steps up to the right, signposted "London Euston" with the BR and London Underground logos. Go up the steps and Euston station is on the right.

Most mapping systems will suggest walking along Euston Road. This is a much more unpleasant walk (along the side of a main road) and considerably further - Google Maps, in particular, can't find the Midland Road entrance to St. Pancras and takes you out through Euston Road, a long walk inside St. Pancras station from the Eurostar platforms.

More generally, St. Pancras is very well connected to rail services for most of England and Scotland - you can use:

• East Midlands Trains to Leicester, Nottingham, Derby and Sheffield from St. Pancras
• Thameslink from St. Pancras (low level) to Brighton
• Virgin Trains East Coast to Leeds, York, Newcastle and Edinburgh and First Capital Connect to Cambridge from King's Cross (across the road)
• Virgin Trains West Coast to Birmingham, Manchester, Liverpool, North Wales and Glasgow from Euston (ten minutes' walk)

There are also Southeastern High-Speed services from St.Pancras (but also from Ebbsfleet and Ashford, which are on Eurostar) to various parts of Kent, like Dover and Folkestone.

The train systems that more difficult to get to because of connections in London are Greater Anglia to Norwich and Ipswich (leaves from Liverpool Street) and Great Western Railway to Bristol, Cardiff, South Wales and South West England (leaves from Paddington), both of which require a London Underground journey to get to the station.

While the combination of Thameslink and Southeastern High-Speed can get you to many places south of London, you might need to get to Victoria (Southern), Waterloo (South West Trains), or one of London Bridge, Charing Cross, Blackfriars or Waterloo East (Southeastern), all of which require a London Underground journey, for some places.

if I want to go to Manchester for example, should I also consider the Eurostar as an option?

Trains to Manchester go from Euston which is a short walk from St Pancras.

So let's see

• ~30m Eurostar checkin BS (less if you buy an expensive ticket)
• ~2h20m Paris to London
• ~20m walking between stations, finding platforms etc
• ~10m waiting for a train to Manchester (more if travelling on an inflexible ticket or travelling at a time of day when trains are less frequent)
• ~2h10m London to Manchester

Total journey time about 5 and a half hours.

Looking at flights it looks like the actual flight is about an hour and a half. Charles de gaul airport recommend arriving at the airport 90 minutes before departure and presumably it will take some time to get out of the airport at the end. So say the total time from entering one airport to leaving the other is about three and a half hours.

If your origin and destination are random points in the Paris and Manchester conurbations and you are prepared to pay for taxis for the final connections and you are flexible about when you travel then I would expect flying to be faster.

On the other hand there may well be situations where the train wins. Trains go to the city center while airports tend to be on the outskirts which is important if your destination is in the city center or if you want to use public transport for final connections. Also both the train and the airlines seem to have substantial gaps in their schedules.