According to the route, day 4 was a "rest day" to explore the island. However, I didn't have time for that, and I saw quite a bit of it while I was looking for the campsite, so I went back to the mainland for day 5.
I left the campsite at 09:50, and reached the port at 10:10; that was a lot quicker than my journey to the campsite the previous evening, mainly because I took a more direct route! I went to the ticket office, where the lady on duty recognised me from the previous day, and she was happy to swap my ticket for the 11:15 ferry (no extra charge). The signs at the port said that vehicles should be there 45 minutes before the scheduled departure time. I wasn't sure whether that applied to bikes as well, but I thought it was best to be there early to play it safe. As it turned out, the ferry didn't arrive until 10:45, and nobody could board until 11:00, so there wasn't much point arriving early. Bikes queued separately to cars, and there weren't many of us.
I got off the ferry in Lorient at 12:10, and reached Guilligomarc'h at 15:10; that was the end of day 5. I passed through Plouay again at 16:15, and it was a bit warmer than the previous day: 25°C on Thursday and 30°C on Friday. In fact, Friday was the hottest day of the week (according to my watch), since it reached 36°C! I made several stops each day in pubs, normally to buy a Coke and refill my water bottles. They all had water on tap, i.e. an extra tap next to the beer pumps rather than just a kitchen tap under the counter for washing glasses. They never charged for that, but if I was going to ask for water and use their loo then it seemed polite to buy something as well. There's typically a bit more small talk in pubs over there, and people would say "Au revoir" or "Bon journee" as I left. In a couple of cases that turned out to be surprisingly accurate, because I wound up going to the same pub again as I headed north back to Gouarec.
When I do LEJOG, I expect that it will be a bit cooler, since I'll be in a different country and cycling a bit earlier in the year (May/June rather than July). I'm also planning to change my eating habits a bit: in France, I tended to have a pastry for breakfast, then a light lunch (maybe bread/cheese or maybe just a snack), and have a bigger dinner in the evening. For LEJOG, I'll be better off having a big breakfast (e.g. Full English or the veggie equivalent) so that I load up on calories in advance.
I reached Priziac at 18:55, which ended day 6 of the route. I felt quite tired, possibly just due to the cumulative effect. The campsite cost €5.20 (€2.50 for me, €2.50 for the pitch, €0.20 tax), and it was nice. It was next to a big lake, and they had various boats available to hire (e.g. pedalloes and canoes). They also had an area roped off for swimming, so I went for a quick dip. The water was surprisingly warm, although it was also quite shallow. Anyway, that was a nice way to cool down after my ride.
When I went to the shower block, I noticed an unfortunate tanline: there was a pale strip about 1cm wide across the top of my forehead! That's the downside to wearing a hat... (I wore my helmet at the start of the week, but abandoned it after a few hours because I was sweating a lot and the roads were very quiet.) Fortunately it's now evened out a bit, so it's not too obvious.
Distance cycled: 73.7km.