uffington sb,
Try this website:
http://www.svalbard.net/index.php?sel=997&lang=0
There is no guarantee to see any polar bears, but there are many alternatives to explore the phantastic nature on Spitsbergen.
On layovers (too few these days) ,the most popular activity for our crews is to rent snow scooters.There are several possibilities of other activities as well.
As the bears for the most part are hard to find, I would recommend a trip up there anyway.
If you are going in the wintertime, I would suggest april/may as the sun is back and the weather is more stable.
Send them an e-mail and I am sure they are more than willing to give you advice.
rgds
A&A