I've never reviewed a play script before, so I don't know exactly what to look for. What I'll do is critique the idea, the flow, and the actual writing because your script needs to be written well in order to get anyone to read it. Hope that's ok!
First, while your descriptions are lush, they sound like they're written from a thesaurus not penned by a normal person. Big, fancy words are not needed. You need the reader to read the words and see the picture you're painting, not have to stop to go to the dictionary in order to figure out what you're talking about. Your words, and the picture in the reader's mind, should flow like the river you're talking about.
Also, while you give very detailed descriptions of the house, not everything is needed. Readers' eyes begin to glaze over when they have to read a bunch of stuff that's not related to the story. Look at the house as if you're driving up the driveway. Describe that. Then, if they're important to the story, describe the inside rooms. You'll see that I don't describe the bedrooms or kitchen because they're not important to the story.
Here's what I got from the first part. I'm not British, so the conversations sound very American, but I wanted to give you an idea of what I mean:
Nestled deep in the heart of the XYZ forest lies a hidden mansion, luxurious in every detail, surrounded by expansive lawns. A secret, known only to a few, the place stands like a trophy shining brightly among trees twisted and tangled from lack of sunlight.
Located only three meters to the north, the Scenic River, surrounded by flowering plants and lush shrubbery, flows quietly, a peaceful reprieve from a clattering world.
For reasons unknown, not one human has set foot on the property in over sixteen years, until three Brits choose it for a month-long holiday meant to blot out the haunting memories of their parents’ deaths. The travel agent who booked the trip was reluctant to provide many details, saying only that she had never seen the listing before it just popped up on her computer screen.
Choosing the mansion for their respite had been simple. No arguments, no debates over which location best suited each brother. The sprawling home surrounded by natural beauty came at a price half the cost of others they had viewed.
Richard, 34, a Physics professor, Mac, 33, a Botany professor, and Donald, 31, a Psychologist, had remained inseparable after moving out of their parents’ home. Meeting at Donald’s house the afternoon of February 11, the trio made the trip together, laughing, talking, and singing to the radio as they travelled further into the forest.
As the car slowed, turning into the driveway, the brothers were speechless, taking in the magnificence of the place.
Donald had always been the skeptical brother.
“There has to be something wrong with this place, for the rental to be so cheap,” Donald said.
“I don’t know what you’re talking about,” quipped Mac. “We really lucked into this deal.”
“I’m sure not going to look a gift horse in the mouth,” Richard added. “I’m just going to enjoy myself!”
By the time they reached the house it was too late to hike down to the river, so they each retired to their bedroom and unpacked. A short time later, they met in the kitchen to grab a sandwich and beer, and make plans for the next day, retiring to bed shortly thereafter.
The next morning, as Richard and Donald busy themselves in the kitchen while Mac decides to take a walk.
“I’ll be back in time for breakfast,” Mac says over his shoulder, as he opens the back door. “I just want to get a better look at all the plants growing around here, so I’m headed down to the river.”
“You’d better be back in time for breakfast,” chirped Richard. “Donald has a great meal planned, and we’re not going to wait for you to devour it!”
As he makes his way down the well-worn path leading from the back door toward the river, Mac is struck by the beauty surrounding him. Colorful flowers spring from lush green plants, scattered along the trail. Running toward the river like a lover catching sight of his mistress, he disappears into the sunlight.
Back at the house, Donald and Richard add the finishing touches to the breakfast feast they happily prepared. But as the clocked ticked half-past ten and they still saw no signs of Mac’s return, Donald begins to worry.
“It’s not like Mac to miss a meal,” he tells Richard as he peered out the window. “I don’t like this at all.”
“Oh, he probably just lost track of time,” Richard replies. “I imagine this place is a wonderland for a Botanist like Mac. I’m betting he headed over to the river. Let’s walk down there and bring him back.”
Write like you speak. Since this story is happening in 2022, in the UK, write like a Brit would talk in today's terms. You want the reader to float over your words, drawing a mental picture of what they're reading, so your words need to flow.
You have such a great imagination! Focus on that, not on trying to use impressive words. In 2022 few people even know what they mean. =)
I hope this helps!