Yes, you should always tell your insurer, current or new, if you have made any claims in the past. Often, when you declare you have made a claim, ‘windscreen claim’ will be shown as an option and you can share the details.

With the others, it's quite difficult for us to answer anything on legal processes as we don't have any insight on these - if we wanted to say something generic, it would be to raise their concerns with their insurer, or if they're not happy they can refer the case to the Financial Ombudsman: www.financial-ombudsman.org.uk/