TVG and Eurorail pass

Covered? Technically yes. Can you hop on and go? No, you need to pay for a reservation, and seats available to Eurail Pass holders can be limited, and can go fast.

Edit: Sorry, saw the TGV, but not your destination of London. That is not a TGV, but Eurostar, a whole separate animal. You would need to go to the Eurostar site to book a reservation, so the advice is basically the same.

If you have not bought your Eurail Pass yet, could you let us know in which countries and when you intend to travel?
Passes are rarely the appropriate option in France, hence my question.

Sorry, about the wrong train name. I meant the Eurostar. We are doing the last section of the El Camino. We fly into Madrid Saturday Sept. 2nd and are to arrive in Sarria on Sunday, September 3rd. I'm trying to do this by train and finding this is not so easy. After Santiago, we are going to visit a friend in Barcelona for three days begining Sept 16.. Note: That visit came up after the El Camino trip was determined and made everything more difficult, but...) From Barcelona we plan to take a train to Bordeaux and rent a car to tour Brittany and Normandy until Sept 25th when we take the Eurostar to London. Visits to various friends in Spain and France are making the travel arrangements for the trip more difficult, but yet making the trip more enjoyable.
So, bottom line, is a Eurorail Global Pass worth it?
Any help with this will be appreciated. This is our first trip to Spain and third to France, but we are considerably older now.

Since you are planning so far in advance, you will probably do much better buying individual rail tickets than a pass.

Thank you.

Spain and France are the worst countries to use Eurail passes.
Both require mandatory seat reservations for passholders, and Spain does not even let you make those reservations online (!!!).
Definitely do not use a pass for your trip, then.

Barcelona to Bordeaux is more convenient with a flight, by the way (unless Barcelona-Toulouse trains resume... they have not resumed yet). Same for Santiago to Barcelona.