Q:Would you please tell me where the shops are to purchase bus saver tickets? Am I able to purchase them online? We arrive late on a Saturday so won’t be able to buy them until the Sunday. This is such a great site and has been so helpful for planning our short 3 day stay. Thankyou.

A:Yes, you can buy London Transport tickets online from some countries. I suggest you have a look at this web page for Transport for London. It provides information on the various types of visitor tickets available.

Judging by your email address, I am guessing that you are in Australia. Here is the link to how to buy tickets online for Aussies.
You can also buy tickets when you arrive, from most newsagents and from any tube station. I think you could even buy them from the airport when you arrive. Or simply go to the nearest tube station on the Sunday morning before you start your sightseeing.