Many times in the past I've changed trains at Lille, I'm not sure i've you've looked into this... Its super easy and only add an extra 30 mins to your journey. Its also usually cheaper!
Try seeing how much it is to book the Eurostar and hotel seporately. I'm guessing here but it sounds like you're trying to book everything through Disneylands website?
I've done this many times:
London St Pancras - Lille
Lille - marne la vallee
The change is super easy! You don't even have to change platforms. You just stand for 10 mins and the next train will arrive.
Marne la vallee - Lille
Lille - London St Pancras
A bit different on the way back. You have to leave the TGV at Lille and go through passport control. But its very easy and well signposted.
Apologies if you've already looked into this but I thought I'd add my thoughts
I did package quotes on the Irish Disneyland site as I'd read tips that would give a better price then the UK site. The Adagio came out at 436 euro cheaper then the Hotel l'Elysee. That's 3 nights, 4 day/2park tickets and breakfast. I'm going to head to tripadvisor for hotel reviews - good to know you're a fan of l'Elysee, I will have to see if it's worth the extra money .
Anyhow, I got a response from Eurostar and they said the timetable won't be released until 16 July. Which is good cause it means it isn't sold out yet and we still should be able to get the train. But, how did all those people on the magic forum board book already? I'm confused!
We paid about AUD $700 total for *5* nights at Hotel l'Elysee! It's one reason I always recommend it - such great value! We went during low season though, and didn't have park tickets included as we got APs.
Phew! Glad to hear you didn't miss out
No worries. I hope you have a lovely time! Also to answer some of your other questions you don't need to pre-book fast pass, still the legacy paper system over here!
ADR are a must for some restaurants - I hear the new ratatouille restaurant is amazing and books up quickly (although yet to visit myself).
Absolutly stay on site! Especially over Christmas, its beautiful. We did Christmas time in the Newport Bay Hotel and it was so pretty!!! Also its much easier to get from the train station (which drops you right outside the parks) to one of the onsite hotels.
Yes its blooming cold here so pack warm! Gloves and hats are a must.
I'm super jealous that you're going to Hong Kong too! My trip is in the planning stages for 2017 so a long time to plan.
And if you're on a budget you can normally save about £20 - £40 per person for a single from London to Marne la Vallee if you stop in Lille but that's up to you as it does add about 30 mins to the travel time.