Fairly frequently we read on here that "I am flying into X and then 2 hours later catching a plane/train to Y". Questioning will reveal that these are two separate tickets and there's a lot of discussion. I wanted to do sum up my recent "good and bad" just to give people a "best case" and "worst case" scenario.
So on March 6th I flew from Atlanta to London. My destination was Paris, but Delta had a "flash" sale to London on business and I got that flight for about the same miles as a normal coach fare. I took the big seat! Now to get to Paris. I did something I would NOT recommend but I decided to risk it. My plane was scheduled to land at 10:50 and I booked a 1:30 train out of St. Pancreas in London. I made it, but.... I had some things in my favor. 1. The plane was early by about 15 minutes. 2. Since I was in Delta's business class I knew I would get a Fast Track pass to skip what could have been a long line in immigration. 3. I know my way around the airport and the London Underground. 4. I traveled carry on only.
I pre-purchased Heathrow Express and bought my Oyster card from my last visit. By taking the Express to Paddington and then the Tube to the train station I was actually at the train station around noon which allowed me time to buy a sandwich before boarding the train.
Now this was a HUGE risk and I actually "self insured" There was another dirt cheap fare on the train leaving late in the evening so I had that ticket in my pocket as a back up and would have stored my luggage at the train station and wandered around London if I had to wait for it.
So my return flight on 3/17 was also out of London. My original plan was to take the train on 3/16 to London.... and then the French went on strike. This created some concerns and issues. Wait times to just get through border controls at the Gard du Nord were running about 4 hours from what I could see and trains were delayed significantly. While I think I could have made my trip to London on 3/16 I wound up buying a new plane ticket to London to protect myself. I did go to Gare du Nord on 3/16 and realized it was a minimum of 4 hours and more likely 5 hours of standing on line (with no food or bathroom breaks as I was by myself with no one to "hold" my spot) Personally I can think of better things to do in Paris! :)
However while investigating I did hear one rather upset family . They had seats on the 8 :00 train. At this point it was 7 AM and they were not really even close to the border control gates and the Eurostar people were still trying to get the 7 AM train passengers through immigration. The 7 Am train had been delayed until 8 and the 8 until 9. However, their big problem... they had a flight out of London around 2 PM that same day! While they still had time it was already getting a little close and there was NO guarantee they were going to make the train they were scheduled for. If they got pushed to the next train (a real possibility) they were going to be doing good to arrive in London by 11:30 which is a little late for a 2 PM flight! They were pleading with the staff to help them, but honestly there was not much that could be done. I am sure that others in front of them had similar concerns and moving one family probably would have started a snowball effect (or riot LOL!)
I just wanted to post this to give people both sides of the story. Yes it can work perfect (see my first flight) and then again it can blow up and cost you money (see the flight I had to buy!)
I did luck out and for reasons unknown to me Eurostar refunded my entire roundtrip when I asked for a refund so my extra flight cost was at least partially covered by that (and I got the flight cost down by buying a round trip .. I will not be taking my return flight to CDG on April 24th :) )