You need to get an affidavit made. This legal document shows who are the beneficiaries of the deceased person. Just contact a solicitor (avoué) and he'll ask you to bring things like:
- Death certificate of your grandma
- Birth certificate and NI card for all persons who claim to be heirs
- Fees for his service
Whatever inheritance there is, you need to show by proof that it belonged to your grandma. So bank details in her name, land/property contracts etc.
If she has registered a will before she died, that may affect how much you inherit if at all.
All heirs need to sign some paperwork. If they are not present, a Power of Attorney (Procuration) would be required for a designated person to sign on behalf.
Note that, sometimes elders may be given preference in some cases. If there's a plot of land to be divided, an elder heir may be able to get the front portion (which can be more valuable) compared to younger ones.
The solicitor will explain everything to you.
Hope that helps.