The use of asbestos wasn’t fully banned in the UK until 1999, so there is a possibility of its presence in your vehicle somewhere, hence the warning label. It doesn’t mean it’s in the bonnet liner specifically though !! Now that you have raised the spectre of asbestos, how you proceed is up to you !! In the building industry, no work is carried out until a survey for asbestos presence has been done. If it is found, or even suspected to be present, all work stops until it is tested/sealed/removed etc by licensed operators.