We are arriving London Heathrow at 9:50 am Oct. 15th on Virgin and plan on go to the Revivals lounge to freshen up and have breakfast. We need to be in Genk at a decent time to be ready for work on the 16 early in the morning. We looked at flights/train combinations and Eurostar/train and it seems the Eurostar/train combination is the most likely option to get there at a decent time. We would like to take the 3:04 pm Eurostar to Brussels, then transfer to the SNCB to Genk. My concerns are: 1) the transfer from Heathrow to St. Pancras station-we prefer the more direct Picadilli line which takes a little longer but it requires no transfers. 2) will we have enough time in Brussels to get the train to Genk? Eurostar arrives at 6ish and the train to Genk leaves at 6:36. Considering we will have luggage (we will be in Europe for 3 weeks, including an 11 day cruise), we want to make this as easy as possible.
What are your concerns getting to St Pancras from Heathrow? It will take you about an hour to get there using the Piccadilly line, but you are correct in that there is no transfer, so I am not sure what your concern is. If you are worried about the time, you could get there faster using the Heathrow Express, but that would involve a transfer. Or if you simply want the easiest way, you could order a car service or take a taxi.
With regards to the Eurostar, I'm wondering why you just don't take an earlier train to Brussels. Taking the 13:01 train would still give you time to relax a bit at the airport, but get you to Brussels earlier and give you plenty of time to get to your destination. It has the added advantage of being less expensive than the 15:04 train. Generally, it would take around 20 to 30 minutes to get from your Eurostar train to the next train to Genk, but that's not considering any delays or anything else that might happen.
If it's important that you get there at a decent time, then I would shoot for the earlier train. Whatever the case, you might want to buy your Eurostar tickets as soon as possible. They are dynamic, so that they go up in price the closer you get to your travel date.
will we have enough time in Brussels to get the train to Genk? Eurostar arrives at 6ish and the train to Genk leaves at 6:36.
Don't worry about this at all. Between Brussels-Midi and Genk, you'll be traveling on an IC (Intercity) train. Your ticket is valid all day and isn't tied to a specific time.
If you miss the 6:36 train, just take the next one an hour later (there's a direct train between the two stations every hour). The trip takes 1 hour and 42 minutes.
In the meantime, you can enjoy a nice meal (or just a drink) at Café Bogard, located inside the station https://maps.app.goo.gl/RD36nPYtqDrZyaSo6