if your licence doesnt say B+E, then you have a standard car licence without trailer entitlement.

You can still tow, but your limited to a few criteria, namely that the gross (plated) weight of the trailer cannot exceed the kerb weight of the tow vehicle, and the gross weight of both the trailer and car combined cannot exceed 3500kg.

If your in that situation, a big 4x4 wont actually be helpful at all, as its gross weight will be very high, usually up around 2700kgs, meaning you could only tow 700kgs or so. Infact a big estate car weighing around 1500kgs with a gross weight of ~2000kg maximises the amount you can tow.

It'll still be fairly tight as to wether you can tow your sierra though, you'll have to do the numbers carefully and see where it lands.

First thing you need is the gross weight and kerb weight of your proposed tow car.