This is from EBay help.http://ocsnext.ebay.co.uk/ocs/sr
What you can change in your listing depends on the listing format, how much time is left in the listing, and if you've received bids or Buy It Now offers.
Generally, you can't change the listing format. For example:
You can't change from an auction-style listing to a fixed price listing.
You can't extend the duration of a listing if two or more hours have passed since you submitted it.
Find out more about restrictions on revising listings.
What do you want to do?
Revise a single listing.
Revise multiple listings at once.