328 wiring issues

Hi I recently purchased a lovely 328 however at some point in its life it obviously had an alarm fitted, it doesn't seem a good job was done at fitting or removing it!

There is a thick blue wire (permanent live) coming out of the main loom which went to the thing in the photo which I assume was something to do with an alarm there was also a blue/red wire attached to it that goes to the driver door and interior light. Where should this thick blue wire from the main loom go and should the blue/red door wire be connected to the thick blue one?
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In addition to this the drivers side passenger window control up button is crudely soldered to a yellow wire of thick gauge the wire from the switch on the door is yellow/red of thinner gauge, this doesn't seem right either?
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There is also a white/red wire of thick gauge coming from a loom connector soldered to a thinner gauge red wire which goes off to the door ...this is switched live with ignition. Obviously I can make a better job of the connection between the two wires it just seems strange how the gauge and colour changes ?
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Thank you