The last time I finished PBP was in 2011. I weighed about 103 Kg, but I can do a 25 mile circuit from my front door that has 2,000 feet of climbing. There was a 10 mile time trial once a week five miles away, except on the third week of the month, when it was a 25. I did the Mersey Roads 24 Hour ride less than a month before the PBP.
The weather conditions are broadly similar in Brittany to Lancashire, perhaps a bit warmer during the day.
So in terms of cycling culture, it's difficult to imagine anywhere more suitable. The rest of the world is open to debate. The Belgians did well, but even they found the cobbled finish a bit odd.