If you are using a trailer within 50 kms of your base or home address you do not need a tachograph.
If you are towing outside of this radius you need a tachograph fitted (if towing for commerial gain) irrespective of the size of trailer and combined vehicle weight.
If you can keep away from towing a trailer for commercial purposes do so - unless you can stay within the permitted radius.
Tachograph regs are an absolute nightmare and you don't get any second chances.
You can have eye hitches and ball hitches I always went for ball hitches because they were fitted and I feel that the eye hitches are more agricultural.
I was pulled more times by the police and VOSA in a twelve month period than I ever have been over all of my previous driving experience.
One VOSA man told me that they actively target van & trailer combinations because they are an easy target!!
You have been warned
Good luck
Rob