Aer Lingus via TUI?

[americanv8]

Anyone flown with Aer Lingus but on a TUI booking? Originally our booking was out of Newcastle in August, in TUI Premium. When that was cancelled I changed it to December but had to fly out of Manchester instead.
MAN-MCO in December is with Aer Lingus, the TUI booking gives a Aer Lingus booking reference and says "Your flights are not with TUI. This means that you will need to go to Aer Lingus's website to select your seats, add passport information, check-in & print boarding pass"
If i do that i get an error message saying "Error Code: DEFAULT. Oops! Something went wrong. Wrong method was used to view this page. If the problem persists, please try again from the homepage."

I spoke to to TUI who said i should be able to use the booking reference they provided, spoke to Aer Lingus and they said nope you can't use that reference to do anything. Can't select seats, etc

I have no idea who's right but Aer Lingus are just ignoring me now.