Q.  Why does the pound coin have a different reverse every year?
A.  The reverse designs go in a cycle and represent the national flowers or symbols of each of the UK members.  There are at least ten designs:

Q.  What does the lettering on the edge of the pound coins say?
A.  There are three letterings: This information taken from Sean's British FAQ.

A better, more complete and up-to-date page with this information is available at UK Decimal Coins.  Also I've cribbed that page here, just in case it gets deleted from Tony's server!   Also at British Coins, backed up here. 1