Train from London to Bayeux

The way most people travel this route is:

Eurostar from London to Gare du Nord in Paris.

Either metro or taxi from Paris Gare du Nord to Paris Gare St. Lazare

Train from Gare St Lazare to Bayeux.

I toured in Normandy with Overlord Tours. They were fantastic.

Either metro or taxi from Paris Gare du Nord to Paris Gare St. Lazare

The RER E line is the most direct, One stop to Hausmann-St Lazare, then underground walkway to the station.
Bus is also an option. But taxi would work best if you have a lot of luggage.

Keep in mind that Bayeux is nowhere near Mont Saint-Michel. So once you get to Bayeux, you will need a car, organized tour or an exceedingly long train ride (with connections).

Thanks for the speedy response.
After researching our options, we have our itinerary planned & booked our hotel & a two day tour with Overlord Tours.