Does anybody have any info on instrument flying in WWII? Did they have ILS or any kind of navaids? Was there any way to land in the weather? Or was the policy just to divert and stay out of the clouds?

A good deal of information on the background of nav aids can be found at this page and this page.

In summary, they used radio ranges and radio beacons from the 20's through the 50's (of course, the NDB is still in use today, in small scale).

VORs came into play in the mid-1940s.

ILS also came into play in the early 1940s.

Keep in mind, though, that these were navaids used in the US. I'm not sure what/if navaids we installed overseas for us to use (or, for that matter, what navaids were already in place).

In the Battle of Britian germans used radio signals in straight lines to steer bombers to their target, a warning signal that saidx minutes till release, then another line that told them when to release. Then of course the british found ways to replicate these signals to confuse the aircrews into bombign the wrong areas