Ifor Williams all the way. brother has got 3 of them, one tipper, two plant, and i regularly tow one to south wales with hay/straw on it and they are a dream to tow with, never snakes (even with 110 bales on it ). spares are plentiful too.
Brian James are a clone of the Ifor's, but IMHO not as well built (they look the same, but it's like the good old fashioned coke/pepsi debate )
One thing to watch though, if you get a flat tyre on an Ifor, buy a new wheel and tyre as there is only about £5 difference (something like £70 for the tyre, and £75 for a wheel with tyre fitted ??)