I am taking a group to London/Paris next year. we only have about 4 days in London and 3 in Paris. How useful are the London Pass and the Paris Museum passes? If they are useful... who is the best company to buy from?
In my opinion, the Paris Musuem pass is well worth it, but add up where you intend to go and see if it will actually save you money. You can buy at any of the participating museums (I suggest purchasing at a less busy museum). The website indicates you can buy online for a hefty additional charge - I'd wait to buy it there. Official website is at http://www.parismuseumpass.com/en/home.php
I personally used the pass a number of times to access museums to bypass the line and also for the sole purpose of using the clean bathrooms. I also went several places I wouldn't have otherwise but they were on the pass.