Kung Plexi-ish rather than JCM800-ish, Plexidrive na nga siguro. The Boss ST-2 at low gain isn't bad either (and it can really jack the gain up real high when you need it, at the expense of some hum of course). BSIAB2 might be ok for you (but I have my doubts -- useful gain range is pretty narrow).
Right now, I have this new old stock Toadworks John Bull Jr. which I got from a shop in Amsterdam a few weeks ago -- just a simple open-sounding (as far as British style overdrives go, anyway) two-knob pedal. I haven't spent a lot of time playing with it yet (mukhang hindi perfect match with my Vox AC30). But you might find something similar to your liking, since you have lots of other tone-shaping pedals on tap.