Just doing a bit of research, do you think I could drive a 3.5t horsebox on my fully comp car insurance? Or is that not allowed and I should have proper horsebox insurance? This is as an owned box, not hired. Thanks!
I think that you would only be insured 3rd party on your box if you did that, it's certainly the case with driving another car. Your box would have to be insured in some way in it's own right (even just 3rd party, fire and theft), otherwise you would be breaking the law.
No.
Most car insurance these days covers for up to 1.5t.
Please do check your policy, it prob covers for other cars (mine does) but not bigger vehicles such as vans..