France, though much bigger than the UK and a bit foreign, is not devoid of hotels. As Wessie says in his excellent advice, France has anything and everything from the very basic Formula1 through to five star luxury, with lots of small family hotels and the homogeneous chains (like Ibis) in between. So, yes, you and your two friends can take pot luck.
As this is your first trip abroad and to France, the first thing you’ll discover is that it’s a much bigger country than it might look on a paper map and definitely much larger than it looks on a computer screen. Talking of computer screens, if you are doing all your planing on a computer, do buy a map or two, too. Why? That’s easy: You won’t have your PC with you on the side of the road. The map that Jazbee suggests is certainly a good one, as are the RiDE links that he and Adventuredon have shared.
To get an idea of the size of France, let’s imagine a journey that goes Le Havre > Brest > Vannes > Nantes > Le Mans > Le Have. In other words, a crude circle through Brittany, Normandy and Pays de Loire, ie the three areas listed in your opening post. It would look something like this:
Google puts the non-stop estimated time as fourteen and a half hours, using motorways. That jumps to a fraction under 24 hours, if you avoid (as you want to) every motorway / toll road. By way of simple comparison: Reading, where you live to the tip of Scotland is just under 12 hours by mototorway and fifteen and a half hours if you avoid motorways and tolls. You now have something to compare with and hopefully can now visualise how big France is. You can also hopefully get an idea how the time jumps if you avoid all motorways and toll roads. We know nothing about you but maybe ask yourself, if you were to ride from Reading to the tip of Scotland (and much further again) would you studiously avoid all motorways and toll roads entirely and seek to ride every small’ish road?
Let’s then look at the same route Le Havre > Brest > Vannes > Nantes > Le Mans > Le Have in the very popular Kurviger app, set to avoid motorways but to also avoid every goat track.
It’s give or take, 1000 miles. By way of simple comparison, that is Reading to John o’Groats and back to Glasgow, just for that one corner of France.
You say you have got a week (7 days) but I wonder if that might include getting from Reading to say Le Havre and back again to Reading. I suggest this only because bods often forget the additional journey times getting from their house and back again. Let’s assume a very modest (very optimistic even) two half days for the Reading out and back bit. You are now at six days to complete 1000 miles, which is about 170 miles each day, taking D roads, in other words avoiding motorways. That is doable. But, again, we know nothing about you or our friends. It might take you all day - every day, rain or shine - to ride 170 miles by the time you have stopped, had a coffee, pressed flowers, had lunch, bought fuel, had a tea stop, pressed more flowers…… and then and only then thought about where you might find a hotel.
But hey, we digress. Your key question was:
The answer is, yes you can and / or you can do both, if you feel like it. The only obvious observation being: if you don’t know where you’ll be, booking too far in advance is bound to be tricky. If by, ‘in advance’, you mean the day or evening before or some time on the actual day, then yes, of course you can. As Wessie observed, things like Booking.com have made life a doddle for the Adventure (with a capital A) motorcyclist. It’s truly a miracle how anyone ever did it before the internet. The dark ages must have been terrifying.
But, as tempting as it might be, don’t just take my word for it. To prove to yourself and your friends that it can be done, enter: ‘Hotels in Brest’ into Google and see how many pop up. Now do the same with ‘Hotels in Nantes’ and see how many pop up. Now zoom in and pick any small town you like in the intended regions of your travels - or anywhere in France, Spain, the UK or America - and ask Google the same question. There might not be any (not
every small French town has a hotel or even a cafe that is definitely open) but the search engines will find you hotels nearby. The rest is now up to you, your chums and your potentially unlimited imaginations.