PS - a big thank you to kybourbon for explaining the Eurostar booking for me. I immediately booked u

I will be traveling space saving travel bags across 4 countries by train. I have found which trains and times (if I've got it right?) and it appears best to buy a pass for myself and 2 adult daughters (both under 25yrs). But I can't work out which one/s? There are so many..... Plus, I am also not sure if a Eurostar space saving travel bags train between London Paris is part of the same European pass package?
The Eurostar from London to Paris is not covered, space saving travel bags but certain railpasses give you a discount on this train. Usually you can find cheaper advance purchase space saving travel bags tickets on www.eurostar.com (price your London/Paris tickets on that link).
Certain trains require you pay a supplement in addition to the cost of the pass such as the TGV, trains between France/Switzerland/Italy and all faster trains in Italy. Some TGV trains have quotas for rail pass holders. You can find advance purchase discounts on the TGV website space saving travel bags (discount fares appear at 90 days out and can sell out). When using French train websites, don't select the US as your country as that makes them rollover to RailEurope which doesn't have the discounted tickets.
For Switzerland, use the Swiss site www.sbb.ch . You might find better prices if you book Thun/Milan on the Swiss site and Milan/Venice on the Italian train website Trenitalia. From Switzerland to Milan you can find some discounted tickets for about 25chf (called Saver on their website) if you select an EC train.
If you only plan to use the faster trains in Italy, price them on Trenitalia's LeFrecce link. You can find Mini Fares as cheap as 9 between major cities and can book 120 days out. Second space saving travel bags class is perfectly fine on these trains as well as on French TGV or the EC trains from Switzerland.
You might try entering your info on railsaver.com . It will tell you whether you should get a pass, but doesn't take into account discounted tickets you can purchase on each country's website. After entering your itinerary (don't include London or London/Paris since it's not part of any pass you would get) and be sure to change the drop-down box that says "always space saving travel bags railpass" to "if less expensive".
PS - a big thank you to kybourbon for explaining the Eurostar booking for me. I immediately booked upon reading your post and it only cost me AUD$46 per person. It definitely pays off to book in advance! You've space saving travel bags done me a great favour!
And as the railpass section explains passes are rarely the bargain they were 30 years ago due to the number of supplements and reservation fees for night fast trains. You may also find that in a country a local pass is better - or even just buying point to point tickets.
In case anyone space saving travel bags else is reading this thread space saving travel bags and wondering the outcome of point to point v passes, I have been working from the the contributions above and found the info absolutely spot on. Passes appear good at face value, space saving travel bags but when balanced with discounts available through point to point, passes are more expensive space saving travel bags and problematic (reservations, limited seats etc).
I understand space saving travel bags the trick to multi train rides in Europe in the current market, is shopping for point to point and well in advance to get the discounts, which are significant. It is also beneficial to compare the cost of a train ticket through each country's train sites. Ie, some countries offer a big discount for the same train not discounted in others.
If you cannot book well in advance, I am not sure if passes might then be the better option because you probably won't find discounted point to point? If you are thinking of a pass at last minute, check to make sure seat allocations are not exhausted and still compare passes by checking what each country offers if you buy from them. info in this thread is really best suited to travelers with time to plan ahead.