A-Frame towing is partially braked due to the weight of the towed car pushing forward making the tracking tow out. I doubt you'd even get a second look TBH.
Not sure you could argue that gives any significant braking, TBH. The law is clear. A trailer over 750kg must have a braking system operated by a hydraulically damped coupling and a parking brake operating on at least 2 road wheels. In addition, a coupling is required to automatically apply the brakes in event of separation of the trailer from the vehicle.
So, regarding the car as a trailer, you're well outside the law regardless of the license you have.
That leaves you towing a "disabled vehicle" "to a place of safety". IMHO.
EDIT: to add... as the towed vehicle is on the road whilst under tow it should officially be taxed and MOT'ed.
Yep. If its' wheels are on the ground it must be road legal.
For the sake of £30 a day a trailer is the more sensible option, IMHO. Bear in mind that the trailer will weigh 500-600 kg though. Personally, I'd
much rather be towing a slightly overweight for the car but properly engineered braked trailer than 1700kg of unbraked, untaxed car on an A-frame.
Towabale weight 2150kg
That sounds high to me. It's only 1850 for the V6 petrol models.
Kevin