A number of county moth groups now have a "what's flying tonight" feature, which shows the species you are most likely to encounter through the year. This can be enormously helpful in trying to narrow down the choices when you are learning to identify moths.
For Berkshire you can download our "Moths by month" document, which lists the moths most likely to be seen each month through the year, and gives a link to the photos and further information at UKmoths. Download the NEW VERSIONS at January 2010:
Common moths through the year - an attempt to show the moths you are most likely to find in your moth-trap in order of when you will see them!
Try out these other sites as well - although most are some distance away from Berkshire, their lists still have a lot in common with ours for the commoner species: