In answer to your questions:
1 - Yes, you can select various currency options including Pounds Sterling as per the payment settings in the ClassiPress admin demo
http://demos.appthemes.com/classipre...ments-settings
2 - You can set the max image size in the ClassiPress admin settings
http://demos.appthemes.com/classipre...s&tab=listings and if the customer tries to upload an image larger than your max, they will receive a message that the file size exceeds the max.
3 - Yes
4 - There is no sort functionality built into ClassiPress, however you can find a sort plugin in the AppThemes marketplace which will allow you to add this:
http://marketplace.appthemes.com/plu...ss-sorted-ads/
5 - Yes, you can set a price per category if you wish. Thanks :)