London to Béziers / Beziers by train

The Eurostar will arrive in Paris at the Gare Du Nord, but the TGV to Béziers will depart from the Gare De Lyon.
This guide explains how to make the transfer between the two stations by RER train.
The London to Béziers tickets do not include the transfer across Paris.

When making a booking, check the connection time between the arrival at Gare Du Nord and the departure from Gare de Lyon; the wide variations in the current end-to-end journey times are mainly to do with the time between the arrival and departures in Paris.
The current, more limited timetables, have compromised the connections, the majority of which now allow around 2hr 30 mins between trains; time enough for a lunch in the fabulous Le Train Bleu restaurant within the Gare De Lyon, or in brasserie by the station.

There are typically quicker end-to-end journeys available on Fridays and Sundays, though be wary of cross Paris transfers of less than an hour; they're perfect if the trains are on time, but don't allow for much contingency in the event of a delay; and there are fewer than the usual number of trains, currently available on the Paris to Béziers route.

USUALLY you can avoid having to make your own way across Paris if you take the alternative journey options via Lille or Marseille, but neither of them are currently an option.

However, there are also 3 ticks in the box for choosing THIS routing via Paris:
(1) More departures to choose from,
(2) you can book the end-to-end journey on one ticket,
(3) and it tends to be cheaper.

Book Early And Save: Yes

Online bookings open: 90 days ahead

Eurostar now DOES sell tickets for London to Beziers journeys by train.
A plus of booking with Eurostar.com is that you can access a 'Manage Your Booking' facility - which enables you to change the seat on the Eurostar, that you will have been automatically assigned when making a booking.
Click on the Eurostar 'train guides’ for more information on how to do this.

The very cheapest tickets tend to sell out particularly quickly on this route via Paris; they're generally more likely to be available if you can travel on a Tuesday - Thursday, or are happy to set off from London early in the morning.

The search results usually combine these journeys via Paris with the alternative connections via Lille or Marseille.
(Avoid choosing 'Beziers Gare Routiere' as a destination - that's the bus station in Beziers).

The ticketing terms:

If you book Standard or Standard Premier tickets, you can exchange them if need be, to an alternative departure on your booked route; but if you want to transfer your ticket to a new departure less than 7 days before your travel date, you will need to pay an admin fee of £30 for Standard Class tickets, £40 for Standard Premier tickets PLUS the price difference with the new ticket you will be booking.
What's new, in response to the pandemic, is that these £30/40 charges aren't applied if you want to transfer to an alternative departure more than seven days before your travel date.

Business Premier tickets are less restrictive, in response to the pandemic they can now be refunded and they can be exchanged to alternative departures without paying the admin fee, or the price difference.
Eurostar's full ticket terms and conditions are here