Yep i have enabled indexing, I ave now installed the latest alpha 5.4 and it has improved performance quite considerably.
Although i notice that when doing a search, roundcube has a 60 second timeout. I watch the imap logs as the search is running and it looks like roundcube stops if it doesn't get a response after 60 seconds. Is there any way to increase this as i cant find it in any of the source files.