I personally never liked the build of Samsung phones, the Galaxy range, until I picked up my S6 model.
Previous ones I thought were always a bit weak feeling.
But I've had solid phones for past few at least, from my Xperia Play which is a solid little thing, to my Chinese gaming phone which were plastic and large but still a solid rugged feel and took drops without damage, then my HTC M7 which was metal and then S6 Edge which was fragile glass but still had a solid feel to it.
The previous Galaxy phones always felt too lightweight for me.
I've not actually seen/held one of these Wileyfox phones myself yet, but they look like they're fairly solid.
I look forward to what the new S7 will be like though in a couple weeks
edit: Just to add, it's specifically the back covers of older Galaxy phones which felt weak, like really thin plastic shell, but the good thing is they're replaceable so could easily throw a new one on if it did crack. Just not very premium feeling to hold