As Richard says, it depends on year, model and spec, but most Focus models were under 1200 kg kerbweight so 1000 - 1100 kg caravan weight would be more realistic. The 1.6 would also be a bit short of power to tow 1200 but should be ok at 1000.
Avondale currently do a 2-berth at 1000kg max but you may need to look to older caravans as they were lighter - this would open up your choice to 4-berths..
Sorry Derek, I did read your post I just forgot to keep brain engaged!
As cars have been getting gradually heavier I'm fairly sure that an Escort will have a lower kerbweight than a Focus so I imagine 1200 kg would be out of the question.
my apologies RogerL is quite correct, I keep forgetting that fords max towing weight is always more than the car, most escorts seem to be around 1096kg so thats the max you can tow but a safe weight would be 85% of that so about 930kg so you will have to choose carefully
if its a focus then it prob weighs around 1170kg so 85% is still around 1000kg but you could go as far as 1170 but dont forget thats total van and contents
I used to own a 1.6 Ford escourt Estate towed a ABI Dalesman with a boat type roof two berth MTPLM 1000kg , to be honest it was heavy going with a head winds lucky to get 50mph on dual carraige way, overtaking anything was a no no, changed to a 2 ltr car problem was solved.