After £1700 in parts, I have now fitted new rear HB shoes plus fitting kit, new rear prop, terrafirma slotted discs and EBC green stuff pads all-round along with two new front aerosus air struts. All seems well for the best part, however I had the arch liner out and when I was putting it back in on driver side i noticed a little fairly exposed electrical block, so

Can anybody tell me what it is and should it have a full cover over it?

Click image to enlarge

Cover for the ABS connector (and pad wear sensor, depending which side)

it just looked like there was a little green board in it and not connectors, but thats fine if that is what it is. So I dont have cover missing then, thats the way they are

Some ABS connectors and blue, some green. So you might just be seeing the green connector. They're quite chunky.