Train tickets through this site?

First choice, the rail company actually running the trains. For Paris to Bruges (Brugge), Thalys ( https://www.thalys.com ), SNCF or Belgian Rail, for Brugge to London, Eurostar ( https://www.eurostar.com select the "any station Belgium" option).
Second choice https://www.thetrainline.com/ or https://loco2.com/ These are European resellers who nave the same prices as the railway companies.
Anybody else is a reseller and liable to charge more and/or not list all trains.

For more info read this webpage: https://www.seat61.com/Europe-train-tickets.htm

"We are a little less than 3 months out from our trip" - good, you still have plenty of time. Any earlier not all tickets are on sale.

After having trouble booking trains through the French official site....oui.sncf (it would not accept my credit card), I very easily booked through trainline. The trains schedule and price was exactly the same as through the official site. I was able to print out the tickets as well as save them through their app so I have them on my phone. It was a very easy process. I highly recommend trainline!

Thank you all for this help!!! I appreciate it!

Loco2 is another good site. Very user-friendly and no booking fees.

https://loco2.com/

Take a look at both sites. I just checked both trainline and loco2. Loco2 did not show all the trains for some reason. Trainline showed the exact schedule that is found on the official French site...oui.sncf and same prices.

I had a similar experience with loco2 and trainline. As others stated, my first preference is the country's own website. On my trip to Spain, I had difficulties with RENFRE. I did purchase one ticket through loco2. I ended up booking the other with trainline because loco2 wasn't finding the route and time I desired. It is my understanding that trainline doesn't always add a fee and when they do, it is small.

When you book through “this” site it really just sends you to www.raileurope.com. I'd take the advice above.