It depends first of all what you consider to be a classic. There are few dealers who sell only Series 1, 2 & 3 Land Rovers, which are what most might view as "classic". Whereas there are others who might view 90s & 110s (i.e.pre-Defender) as classics, in which case there a few independents you could consider.
Secondly, where's up North? Based on where I currently live, my neighbours get nose bleeds if they travel past Watford Gap, but from my birthplace Newcastle and upwards was "Up North".
In the end you may find you end up travelling quite a distance to look at, and buy, the right one for you. I ended up driving 120 miles to buy mine, and it's only 7 years old, so not even a classic.
Tazz