Do some proper research, doesn't matter if a car 'tows it fine', it has to be legal! Published towing figures are based on how heavy a trailer the car can pull away with on a 12% gradient so it is quite a good guide to what they will cope with (though not a guide of stability)
Ford Mondeo TDCi 130 will tow 1800kg though I've heard the rear suspension can sag a bit so might want to get one of the nicer versions will the self levelling rear shocks.
Mondeo's towing weight is regarded as excellent for an Estate, I think the other contenders are RWD BMWs/Mercs.
whattowcar.com says estates and hatchbacks for 2000kg trailer, Audi S6, BMW 5 series, Mondeo 2.2TDCi (176bhp) and 2.0TDCi Auto, some 4×4 versions of the Skoda Superb and VW Passat, Subaru Outback IV (3.2 Auto) Volvo XC70 and V70. These are current models, you can search back to older years as well. Either way, you are looking at the biggest and most powerful estate cars you can find.
Bump the weight up to the next option, 2500kg, you are looking exclusively at large 4x4s.
To work out the towing weight for the car, deduct the gross train weight (first and highest number on VIN plate) from the max gross weight of the car (second number on the VIN plate).
If you are towing sheep I guess you have quite a meaty trailer, unlikely to be under 1200kg empty and probably has a max weight of something like 2500-3000kg if its a livestock trailer or horsebox?