Just watching the Radford's vlogs from the place.
Firstly, they've stated the villa they stayed in had been gifted (Sue even started the vlog by mentioning this also). They wanted them to try the new accommodation that sleeps 24. They had an entire vlog dedicated to showing the accomodation. Their second vlog showed the entire theme park. Basically, they showed everything and seemed to have a really good time.
From their Instagram, I've figured out their food was also gifted (the birthday meal for their 3 year old has #gifted ). Lots and lots of pics, and then a competition in collaboration with them to win a holiday.
Duinrell also posted a pic of the Radford's on their Facebook page whilst they were staying there.
Sorry, that was quite long winded. So, what I personally think has happened is the Minghams reached out to Duinrell after jealously seeing the Radford's gifted holiday, started their long bullshit conversations saying how amazing they were and how many views they get etc. Duinrell perhaps offered to gift them the accomodation but they had to pay for everything else (food, water park, pool, theme park). Sarah being the jealous bitch that she is decides to act bitter the whole time they're there and slag it off because she didn't get enough freebies. Perhaps they expected the whole thing to be gifted, and then they told them they had to pay for food and extras? That would explain the awkward first dinner.
Just my thoughts anyway. They definitely didn't get the same treatment as the Radford's.