Hi
@Walkingboy - I was so carried away going on about the general case for walking trips in Britain I overlooked answering your specific request for a comparison between the C2C in northern England and the Frances in northern Spain.
I was making the case, based on four trips, that just about any long distance walking trips in Britain are more difficult, by a significant multiple, than the Frances by reason of the relative lack of adequate infrastructure at reasonable intervals, whether or not it is moderately priced, in Britain. While on the Frances very adequate and reasonably priced accommodation is available in most cities, towns and villages along the Frances: and often there is a choice, even in small villages.
The points of difficulty for the Frances are the 2 ascents of note and three singularly difficult descents.
The first ascent of note is from Saint-Jean to Col Lepoeder. This starts at 170 metres above sea level (asl) and you attain 1430 m asl, a 1260 m climb, over 18.5 km = around 7 % on average: the average is significantly exceeded in the 8 km pull up to Orisson.
The second ascent of note is from Les Herrias (about 45 km west from Ponferrada) at 650 m to La Laguna at 1200 m, a 550 m climb, over 5.5 km = 10 % on average.
The first potentially difficult descent is from Col Lepoeder at 1430 m to Roncesvalles at 950 m, or 480 m down, over 7.5 km = around 7 % on average through a forest.
The second is from Alt del Perdon (about 13 km west of Pamplona) at 770 m to Uterga at about 500, or 270 m down, over 3 km = around 10 % on average over an extremely difficult surface.
And the third is from Col de las Antenna (about 80km west of Astorga) at 1515 m to Molinaseca at 590 m, or 925 m down, over 14 km = around 6 % on average but over some difficult surfaces.
There are other equally sharp rises and falls but of much shorter duration and/or easier surfaces.
While the quality of the tracks for the Frances are in the eye of the beholder they do allow daily distances of 40 km or more on a regular basis for those who want to do that. And completions of around 25 days for the whole 800 km are not unknown. Over two sessions in May 2016, I retired hurt at Estella and restarted from there in October 2017, I completed in 27 days walking (not including rest days) when aged 74/75.
So, although I have not attempted the C2C in northern England I hope I have given a flavour of the Frances from which you can make your own comparison.
Be pleased to answer any questions.
Kia kaha (take care, be strong, get going)