To keep practising after the class you need music so get online and but some! Amazon.co.uk have a vast selection - just type 'Salsa' into the search box.
 

Beginner's Guide to Salsa Vol.1 [Box set] £5.97 at Amazon

Simply Salsa [Box set]  
4 CDs for £8.99 at Amazon

Baloba  
Salsa with an African Twist£12.99 at Amazon

DVDs

There is no substitute for learning with a teacher and other people but DVDs can help you improve at home between classes. The samples below are not an endorsement, merely a taste of what is available
 

£10.99 at Amazon

£14.99 at Amazon

£9.03 at Amazon