i've done the Beatles Story museum on the Albert Dock. It's acutually a lot of fun, but a little expensive. I remember it being like 15 pounds/person but I could be wrong.
Just checked on the pricing - it's £8.99 - so probably around $19. Think I should book ahead? Yesterday, I booked the Robert Cains Brewery Tour & Magical Mystery Tour - because it seems as though they both likely sell-out and both are held just once a day. The Beatles Tour was the pricey one at £12.95. There's apparently a Casbah Coffee Club http://www.casbahcoffeeclub.com/ Tour, but that one's like 15 quid & I don't know if I can fit it in. I'll see.