I have a trip sort of booked. Well, the time is booked from work and I have paid a deposit on a ferry. Wed 18 Sept out from Portsmouth at 12 noon. Arrive Bilbao 12.45 day after. Home from Santander on 29 Sept 17.15 to Portsmouth on 30 Sept at 20.45
Hotels only. Vary from Paradors at £100+ per night to a pension where half board is 50 euros a night. I prefer to book 2-3 nights in one place and then tour the area.
Probably do a bit in SW France to start and then cross into Spain on the N260 etc. Quite happy for someone to tag along. Due to the terrain, daily mileage is unlikely to exceed 300 miles and maybe just 150.
Even on group trips I might decide to travel solo during the day so you would need to be able to find a pre-arranged rendezvous such as a pre-booked hotel. Having done many group trips, some I organised, some by others here or even commercial groups, I find everyone has different preferences in terms of stops for photos, food, fuel range, stamina ad infinitum. It's nice to have company when dining.