I have a friend who is in need of some legal advice.....?

Now I have a mate who has been arrested for attempted murder and has been questioned and bailed to appear back at a police station at certain date. What he would like to know is if the police had some concrete evidence would they come and arrest him or would they wait until the bail date is due and then press charges then. Clearly there was not evidence at the time to hold him otherwise he wouldn't of been allowed to talk to me or anyone else for that matter. Just would like to help him as much as possible. Also people have told him that saying "no comment" makes him look guilty and I can see why however he claims its the advice that was given to him be his solicitor.

Thanks guys!!