Discovery 2 Flashing B

Hi, I have a discovery 2 td5 facelift 2003. I’ve changed the power steering pump and pipes and gone to start it and there is a flashing b on the dash. There is condensation in the fuse box drivers side and the roof lining is wet so I know I need to stop the water getting in.

I’ve tried starting the car but I have to lock it and unlock it for the red light on dash to go off but can’t and the horn comes on twice as if a door isn’t shut. I’ve got the flashing b in the dash.

Any ideas what the flashing b is please as I’ve not seen this before and is this stopping me from being able to start it?

The flashing B is not a good sign. You have a buggered fuse box, BCU or similar. Water being in the fuse box is bad news really as that tends to corrode the boards.
If it were me id fix the water ingress, dry all wet electrics, open bcu and inspect for damage and same on fuse boards. You may be able to clean things up with isopropyl alcohol.