I doubt very much whether the garage has a legal responsibility here. In the same way that you would read your handbook and take the car to be serviced at the appropriate intervals, you would expect an owner to be aware of things like cambelt changes.

If you're going to have the work done find a good independent place - it'll be cheaper.

I think it is only in fairly recent years that makers have put cambelt change recommendations in handbooks. Can't speak for Ford, but when Peugeot switched from chain to belt in the 205 about 1987, it was many years before dealers were given advice to change them at 48K, and I don't think it ever appeared in any handbook. To begin with I don't think they really knew how long they might last. My daughter suffered a failed belt not long after her car was dealer-serviced at 50K. Nothing had been said.

And Renault Clio servicing schedules didn't even include coolant changes for a long time, almost as important in the long term.