Probate still not submitted >12 months

The testator must have had good reason for choosing the executor, and trusted them to do a good job. You say you have a good relationship with the executor. So my suggestion is that you offer to help with the executorship and request that they set up a meeting with the solicitor to discuss how preparing the probate application is going and bring you along. This way you can ask all the questions you like, and the executor can give the solicitor on the spot permission for them to answer you directly. If it turns out the solicitor is waiting for documents from the executor volunteer to assist the executor. This way you will know what has been done, what needs to happen next and be up to date on progress.

I see you have edited all your posts so I am not sure if I am missing something crucial, so if my suggestion is not a runner then @DannyBoyD suggestions above are the only way to go.