[spiderserie4]

if your car has an aftermarket alarm, look at that (I can spot an odd "button" thingy on the fuse box cover in your photo, that looks aftermarket for a start)...they can go bad and drain
100mA is a lot....should be 10-20mA (clock and radio memory)
A bad diode in the alternator can also allow a drain

but, as above, the prime suspect is the footwell lights getting kicked on when leaving the car....you could pull the light timer relay (the big one marked 0679, 3rd along from left) then see if the drain goes.

 

[spiderserie4]

Yes. I found a reference to the button

never seen that button, I must admit.
you found a reference to it in the shop manual?
what does it say? photo of page?

 

[spiderserie4]

By the way, I am down to normal 10 mAmp drain. I'm sure it was related to the mess in the fuze box.

well, that is good!