last "whats this for" on electrics

[pug306driver]

Under bonnet fuse box, there seem to be a relay? missing from the roundish grey terminal socket in the picture, also whats the small black box at the top for please?? 

The fuse in the extra fuse holder is for the tow bar plug/caravan plug, not that i have a caravan!!

Also just in front of the fuse box, there is a large black plastic long terminal box thats cable tied together, tucked in quite tight under the wing joint area,     whats that for please???

[Toms306]

Not sure what that grey ones for, it's always empty on HDi's that I can remember.

[Sambarker]

Yeah mine is also empty

[pug306driver]

Cool, but what does the black little box at the top of the picture do/control. Looks as if it has a brown, a white and a green wire going to it.

It was damp ( well it rains a lot here all the bloody time!! ) on the way back from mot on a back road so tried the brakes for anti lock, it works, r/h/side skidded at about 30mph, released and reapplied, so the system works. Only a very momentary kick back on the pedal. First time skid in this car, even deliberately.