There is no such thing as a "Safe" Towing weight for any car. Safety is down to much more than just a set of weights, but the caravan industry recommend that novice caravanners should not have a caravans maximum weight greater than about 85% of the tow-cars kerbweight.
This is all very imprecise, and for reasons that I won't expand here quite contentious, but the industry guidance is at least a starting point. It is always a good idea to keep a trailers weight as small as possible and never to exceed the tow-cars specified maximum towing weight.
it seems that the 2007-10 Ford Mondeo 1.8 tdci has a typical kerbweight of about 1500Kg. Based in the industry recommendation that means a novice caravanner should only contemplate a caravan with an MTPLM of 1275kg. This well within the specified capability of the car.