Confusion. Very many issues with their website.

Doesn't accept non-UK addresses and phone numbers for credit cards on the website or one the phone (since not all billing addresses have a UK postcode!) - a little disappointing for a travel company that might be expected to acknowledge the existence of international families trying to arrange travel together.
You can't login with your booking references at: www_tui_co_uk
but you can at www_marellaexcursionspassenger_tui_co_uk/itinerary

Utterly confusing!