I'd advise against it. It cannot cause an obstruction, and occupying a designated parking place may constitute an obstruction. You may get a letter from the LA if a neighbour complains, demanding that you move it.
The caravan's reflectors must face the direction of the traffic. The police say that a caravan must be lit at night if it is parked on a road and comply with the other normal parking rules. You'll probably meet this definition if your caravan has all the normal regulation reflectors and is parked near street lighting.
You might not be covered by insurance though.
If you try and sleep in it (I'm assuming this is proposed to be a regular occurrence) the LA are likely to take a dim view.