I had a very wilful DD, who, I often felt, had read all the baby books in the womb and knew all about this naughty step/discuss behaviour with her etc etc type discipline, and treated it with contempt. In the end I started withdrawing privileges/mild bribery.
On holiday, it could be a statement before going to the supermarket such as 'If you behave properly here and do not run away from M &D, we will go to the park and have an ice cream.' If she does run away, this treat is cancelled. There will, of course, be an almighty tantrum. This should be ignored, no pleading with or trying to placate. Just ignore it and talk among yourselves until she calms down and the day can continue.
It will take time, but she will eventually get the message.
Like others I must admit that a 4-5 year old on holiday in a cottage with her parents, all her toys and books at home, is going to get very bored. Her parents should be including one child orientated activity into their holiday every day.
We had this type of holiday, but always made sure that DC's interests and occupation were catered for. There are plenty of child based activities and other attractions she may enjoy; animal parks, train rides, children's playing grounds etc. There will be plenty of leaflets, possibly in the house, but certainly at the local Information Office.
How do you acknowledge Easter.
Just how much taxpayers money have the Tories wasted