All new and infrequent sellers are given limits to protect them, buyers and eBay from potentially fraudulent buyers/sellers and fake accounts. The limit is usually 10 items or £650, which ever is used first.
The restriction is in place until you prove (by meeting eBay criteria, such as feedback as a seller, posting out on time and returns rate if any) that you are a reliable seller. You do this by having trouble free sales, good feedback and no policy violations.
In theory you can apply for an increase after 45 days selling on eBay, but it often takes 90 days to meet the eBay requirement. Details of the policy, a link to check your current selling limit and a link to request an increase can be found on this eBay page:
http://pages.ebay.co.uk/help/sell/sellinglimits.html
Just a heads up as regards your current listings - if you list an item at 99p and it sells for 99p you may find yourself with very little profit - eBay take 12.8% of the total amount you receive (item price and postage price) plus 30p.
