Can anyone put me right? We are still toying with the idea of towing our car behind on longer trips away, having look into it as best I can prices seem to vary between £ 2,500 and £850 for the job to be done . Surely there can't be such a variance in price for basically the same product ? Now here's were I'm really confused , some companies are telling me overrun brakes are illegal and the brake servo has to operate whilst another one states quite correctly I suppose that caravans do not have a servo. I am a mechanic and fully understand the servo is there to aid the driver and not the brakes , so you will achieve braking efficiency but you have to push a whole lot harder to get it . Having googled trailer regs etc it only seems to state over750kg must be braked and all wheels/ axles on the road must have a working brake, I can't find any mention of efficiency or servo , so does anyone know for sure or can you point me to a site that does ? Thanks