The way I understand it, the rights of direct family members of EEA citizens flow directly from their relationship and hence they have the right to stay with the EEA citizen in the UK even without any documentation.
However, the rights of an EFM only start after they are certified by the Home Office by the issuance of a Residence Card (not CoA).
Page 25 of the
Processes and procedures for EEA documentation applications states;
The COA does not confirm that the holder has a right of residence in the UK:
a‘short’ COA confirms receipt of the holder’s application.It does not confirm any right to work for the applicant
Page 30 of the same document states;
Extended family members, including durable partners, of EEA nationals do not enjoy an automatic right of residence in the UK until they have been issued with a document by the Home Office confirming such a right.
So, between the time of the end of your T5 visa and the grant of a Residence Card, I believe that you will be an overstayer.
To avoid this having a negative impact on any future application, such as naturalisation, I would suggest leaving the UK before the end of your T5 visa.
Remember that Section 3C leave does not apply to applications made under the EEA regulations. You are dealing with two completely separate systems of law here and the rules of one do not apply to the other.
As an aside: can I suggest to the mods to move this thread to the EEA-Route Applications forums?
PS: Just to clarify, the 28 days of grace at the end of the visa apply to future
immigration applications under the UK Immigration Rules. You would still be an overstayer from the day the visa expired and that would be accounted for in any future naturalisation application or applications under the EEA Regulations, both of which implement different laws and definitions.
I am not a lawyer or immigration advisor. My statements/comments do not constitute legal advice. E&OE. Please do not PM me for advice.