The Blenie is not flyable but I guess it will eventually be made flyable. The Bf110 is already available.

Just equip them with a night fighter skin and bingo, there it is.

You can also use the Hurricane which served as a night fighter (I also think the Defiant too but this is again a non flyable plane)

The only problem that I currently see is that (and I have tried it) it is really pitch black when at night. Even with the moon out (while the full moon does give some light allowing to distinguish things at least on the grey scale) it is pitch dark. You do not see a damn thing.

To my knowledge board mounted radar was not existing yet (or does anybody have information about that it was already implemented).

Ground based radar was to my knowledge not that precise to guide a fighter to enemy bombers. As far as I remember some reading the visual encounter during night was really by chance during the early stages of the war and not very effective. Perhaps over a town or an airfield with working flash lights it could work to have some night fighter missions.