wont turn over headlights on and cooling fan running

I have a strange fault on My Nissan Micra 2003 petrol 998cc.65hp (it’s the K12) . On my way home the electric windows would not work and the indicators where not working. Car was running fine. Now the car wont turn over. Dash lights are all on they don’t dim / go off when I try to turn it over. And the head lights are on (although the switch it turned too off they come on with ignition) And the cooling fan is running with the ignition on Any help appreciated
I'm not an expert but I'd start by checking the battery and then ground connections. I think there is an overlap in modules that control/power what you have mentioned Body Control Module (BCM) for windows/indicators/headlights and Intelligent Power Distribution Module (IPDM) for the headlights/cooling fan/starter and probably more modules. So as its impacting several modules / functions it feels like it could be a common problem like battery / ground.
I also assume there are no error lights on the dashboard and it could do with a code scan to see if there are any errors logged.
Thanks for the reply Checked the battery and its giving a constant 12.8 volts. Checked all the wiring harness and cannot see any loose connections. Took of all the earth straps too the chaise and cleaned them all and tested them they have continuity. Took out the ignition switch barrel and checked its sending power where it should and that seem ok …..stumped now
I would say the next step would be to plug it into an OBDII diagnostic tool to see if there are any fault codes and if the modules are all talking to each other. I'm not sure of the decent cheaper options to do this on Nissans e.g. elm327 adapter and some software. I have used NDSII lite (v1.53) with an existing bluetooth elm327 adapter on my families k12's. Although I've not used extensively it can show certain PIDs, fault codes and appears to have some self diag feature although i found it a bit flaky when trying to connect to my bluetooth elm327. Any decent auto electrician should have much better equipment to diagnose this if you went the garage route.

Of course you could also try disconnecting the battery for half an hour to see if that fixes it by resetting the modules (although you might have effectively done that when cleaning up the chassis ground connections.)

Edit : Also try the K12 Owners UK group on facebook someone on there might have experienced something similar.
Got an OBD2 reader goes though the loading protocols and it says it cant communicate looked on the web and checked the supply voltage and earth to the port pins and they are ok disconnected the sensors one by one as one of the vids said it might be one of them throwing it out with a short but no luck thinking it might be the unit is just bad so it’s a scrap