Alex
Nothing against your theory as such, but the problem is that 229 Sq was based in Malta, where it recently had reformed.
I have no reports that this unit was used over Tunisia. Rather it was used for defence and later for offensive missions over Sicily and surrounding areas. However having said that, Shores mentions 229 Sq in connection with possible Tunisian activities on 17.1.43 (one aircraft making for the Tunisian coast short on fuel), but only then.
My bet is still with ER820
Cheers
Stig