I've now completed several multi-day walks. At some point I plan to walk across Britain on the Coast to Coast path. I've walked across Spain and Gran Canaria. Maybe I should write those up on my blog...
There are a lot of good long distance walks in the UK. Not having done the coast-to-coast personally, I will say I've heard from various people that the part in the middle of the country is less interesting than the two ends given the highways etc.