Idea for a new horror movie

In the heart of the yorkshire dales during summer half term a small group of teenagers, who are fifteen and sixteen years old decide to go camping.
The main character Lucy is the popular girl of the group and was her idea to take an adventure for a few days. Everything begins to be normal. They manage to set up their tents and collect firewood. During their first night they all have a party and drink to the early hours of the normal.
As the next day starts, strange things begin to unfold. A couple of the group, Toby and Lucy who leave the campsite for more firewood begin to hear quite frightening voices softly whispering things like "we are only just behind you" and "you will not live past the night".
The pair of them run back to the campsite to report what had happened. The rest of the group just play it off as a joke to scare them all. Toby and Lucy are in genuine fear of their lives and purposefully decide to stay up for the whole night at the campsite. Nothing seems to develop during that night, to the surprise of the fearful pair and were humiliated by the fact that they had no sleep.
Whilst the pair come to the conclusion that nothing is going wrong, they go to sleep in their tents. Meanwhile the rest of the group head awayfrom the campsite to see if they can find something interesting to do at the local tourist office.
Later that day Toby and Lucy wake up from their sleep to discover that all of their friends have left the camp. In search of their friends, they realise something seriously bad has happened. they start to find clues telling them that their friends are dead. They find pieces of their friends clothing with writing written in blood. Seeing this the pair sprint back to their campsite to collect their belongings. Unknowing to Toby and Lucy, the villain has been waiting at the camp for them. Whilst Toby is finishing to pack up his rucksack the villain comes from behind and stabs him in the back. As this happened Lucy has been busy packing up her own bag next to her tent. As the villain moves towards her, she sees a shadow on the floor of a hand with a jagged blade. Lucy nervously lowers both her hands towards a large piece of wood on the floor and swiftly turns and smacks the villain over the head. She then grabs the blade the villain had. Lucy doesn't know that she still hasn't escaped the terror that has been placed upon her. Or if she managed to kill the villain now on the floor.