From personal experience, Mountain Warehouse backpacks offer solid value for budget-friendly hiking adventures. I have used one of their mid-range models on several day hikes, and it has held up well against wear and tear. The "Trek" series is particularly popular due to its affordability and practical features like multiple compartments and water resistance, which are handy for organizing gear and handling light rain.
In terms of comfort and durability, they're generally good, but it’s always worth considering how much you’ll push the limits in terms of weight and usage frequency. For longer hikes, make sure the backpack has adequate padding and support. It's worthwhile to go to a store, if possible, to try different models on and see how they feel with a bit of weight in them.
Looking at other brands, Decathlon's Quechua Forclaz range could be another great option. They are fairly priced and often recommended for their comfort and quality. I found the harness system in a Quechua backpack to be quite supportive, which makes a difference on those longer treks.
Once you narrow down your options, check reviews specific to your intended use, such as multiday hikes or day trips, as product performance can vary. Happy trails on your hiking adventures!