Pre-heat the grill and line a grill pan with some foil.
Prepare the cous-cous as per the instructions on the side of the package, if you want to be naughty then add a little butter to the water added.
Rub the mackerel fillets all over with the olive oil, and place onto the grill tray skin side up
Place half of the prepared cos-cous onto each plate, lay the fish over the cops-cous, one piece skin side up the other skin side down. Drizzle with the lime and heap generous dollop of peppy piccalilli onto the top of the fish.