“…whereas most people stop on a motorway to use the free facilities.”
There’s nothing remotely “free” about them bhg. Motorists contribute huge sums to the Exchequer in the form of Vehicle Excise Licences, Fuel Duty and VAT (which is even levied on the Fuel Duty making it 20% higher than published). The least the government can do in return for these vast sums is to provide funding for a bog and a lightbulb at motorway service areas rather than rely on BP, Burger King and Costa Coffee to up their prices to maintain them.
In France, Spain, Portugal, Italy, Germany and a few other continental countries they have what are called “Aires”. These are rest areas and they are provided at quite frequent intervals. They are simply car parks with toilets and usually a picnic area so that you can stop, use the ablutions and stretch your legs. Many of them allow overnight parking of caravans and campervans. There are no shops so no enticement to spend money to support the “free” facilities and they are funded by the government.