Thank you for the question. If the passport office are not willing to give the passport and the grandparents are not willing to cooperate, you can take legal action to resolve the matter. Firstly, I would write to them and state that if they do not give you permission to use their certificates, you will take legal action to obtain these, this may make them more willing to do the right thing. However if that is not the case, you can take the matter to court and obtain an order which will require them to do so. Once this is executed it should solve the issue.
I shall provide you with a helpful link that will assist you in finding a solicitor/representative near your local area. This will provide you with someone nearby your area who can assist you if required.
I hope this information proved helpful. You will find a local solicitor who deals with these matters on the law society webpage which is as follows;
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