The concept is well imagined and it seems to be aiming at an older audience. Curiously the first two episodes had a zero body count, then they suddenly seemed to change their mind and the bodies started stacking up.
The largely unknown actors put in pretty good performances. Surprisingly ex "S Club 7" member Hannah Spearritt is a capable actress. The DVD extras reveal she is less capable at throwing rocks though - the one she was meant to throw at a creature hits the cameraman! The CGI effects are excellent for a TV series with a strictly limited budget, almost film standard largely thanks to the previous ground breaking Walking With Dinosaurs, with only the occasional wobble.
However while the overall story is engaging the script writer ought to be fired for the details. Our belief in the characters is disrupted at regular intervals when they do something unbelievably stupid just to keep the story running. For example when being told to run for the trees the character can be clearly seen running along side them, and after armed special forces are driven off by creatures they are content to let unarmed scientists face them alone, not intervening even when hearing they are in trouble on the radio. Every episode has such incidents which require forceful suspension of belief.
The characters also need to be developed more and their strengths played to to justify their continued participation in the project, as some of them are tenuous.
Despite these script failings the series shows a huge amount of promise and I am delighted to hear a second series has been commissioned which I will certainly be watching.
I recommend you give it a try. You may be surprised.