From the manual (Which one assumes you have read, but forgotten)
"The interior light flashes: The refrigerator door has remained open for more than two minutes. This is not a fault but a warning to close the refrigerator door."
That suggests there is something more than a simple switch circuit driving the lamp.
I did a search for the door switch and found this:
http://www.yourspares.co.uk/parts/hotpoint/fridges-and-freezers/ffp187mp/parts/ys39177/hotpoint-ffp187mp-magnetic-switch-door-stop-15x10x5-C00075612.aspx
The door switch is a magnetic switch - which is why you couldn't see anything as it is inside the moulding.. Part number is C00075612.
I found a reference to that part in this manual:
http://www.visynet.be/schemas/AR/BMBL1812F/doc.pdf
I suspect this operates similarly to your own . The switch seems to be connected to a PCB, which also drives the interior lamp.
You will need to do a little sleuthing and some diagnostics. Should be easy enough.
Anon, June 2016
