I ride various tires, 28, 35, 38, 45 and while different tires ride differently, regular marathon 35s which I have on one bike, ride well enough.
im not familiar with your contis, but I strongly suspect you'll appreciate and notice the bike is quicker, less effort for same speed with the 35s vs 47s.
the 35s also do a good job on rough tarmac, of which we have a lot of here in Montreal.
sounds like a great ride, never got to ride in Wales when I had family living there.