Hello Rawky mate. It's great to see you got your project underway, I'm well impressed. I just watched the trailer twice and here are my observations. Generally I thought it was good. I agree the heartbeats should be phased in slowly. I thought they were too loud for the dialogue at the beginning, a bit too intrusive.
I didn't like the sliding text narrative it looked a bit tacky. White text on black looks good but I would have the text static and fade it in and out. I also thought it was a bit disjointed. I would have most of if not all the text at the beginning because it's kind of distracting coming in and out during the trailer.
The actors: I liked them all except the one in the jacket. I think it's Tom? He's asked to introduce himself at the beginning of the trailer. He is over-acting bigtime. I'd ask him to tone it down a bit the scenes with him are really jarring. The girls are great, particularly the one that plays Jessica. I would give her a lot of screen time if it was my choice. She's very natural.
I really liked the flashing imagery at the end it's very effective and it's a great way to end the trailer. I like the movie name lingering at the end too. Oh, and it's a good name for a film too, definitely keep that title. It's a great start for you, it's hard to believe this is your first attempt at a trailer. With a bit of work it could be very good indeed.
Well done Rawky it's an excellent start. All the very best of luck with it, I'll be popping in to keep an eye on your progress