A friend and I rode across England, Ireland, France, Spain, Portugal and Italy many years ago, a total of about 4000 miles.
We mostly slept in whatever sheep pasture, horse paddock, orchard, city park, cemetery or forest preserve we could find around dusk. A few people took pity on us and let us sleep in a barn or garage, and we scored a couple of $7 hotels here and there.
The bikes held up well, but we went through a few weeks of multiple flats per day because of an incompatibility between some rims we bought in France and the Spanish inner tubes. Maddening. We also wore out many tires and a few chains.
As for training, that was England.