Have you completed the purchase of the house? You need to have building insurance from exchange because you are liable for costs from that moment. It’s like car insurance, it’s not an optional nice to have.
Buildings insurance is the cost of something happens to your house to rebuild it, you will still owe the amount on your mortgage. You will still be paying your mortgage so where would you find the funds to rent a new place or rebuild your home? It covers you for flood and fire but it also covers you if someone drunkenly drives into your front room, a tree falls on your roof, the property is subject to subsidence.
Contents does push up the premium but I would argue it’s also essential. It’s not about the quality of those things but it’s if you have to replace those all in one go. So if your home had a fire, the fire might be relatively well contained to the back of the house but you’ll likely still have smoke and water damage throughout. You’ll be paying for a new kitchen to be put in, buying new plates, new pans, new washing machine, new fridge, new towels, new bedding, replacing your wardrobe, replacing your couch, your desk, the beds, the curtains, rugs, new flooring. You’ll be replacing your pictures on the wall. You might be replacing a bike, depending on where it is stored, your lawnmower. Even things you wouldn’t think of like the ironing board and iron. You’ve been given some stuff because people have those to hand but people won’t have an entire house and wardrobe to hand. If you need to buy these new, how much would it cost you to replace everything in your house?