Well I'm in Norfolk at the moment and this cottage is really good. Plentiful supplies, loo roll, toiletries, cleaning supplies, soft towels. Never seen one as generous as this before. Also tea and (instant) coffee, sugar, oil, salt & pepper. A welcome basket with a pint of milk, nice cookies and a jar of home made jam. Space in the cupboards, and enough (8-12 for occupancy of 4-5) of cutlery and crockery, large mugs, 3 sizes of plates, 3 of bowls and even a cast iron casserole (and a Cafétiere, but I had to supply the ground coffee). The knives are sharp (ish). Comfy furniture, plenty of seats for everyone. Ok I'll stop, I did choose with care and it's not cheap. Broadband is good (at least good enough for 4 simultaneous users two of whom are watching YouTube) but phone reception nil (we were warned).
Minor niggles: light curtains without blackout lining, and motion detector switches in the bathroom, which are really handy but go off after 30sec, so if I sit down and relax a bit for a moment I end up in the dark and have to wave my hand to switch it back on. Could do with a few more serving / larger bowls in the kitchen. But I am being nitpicky now.
I'm always very careful to scrutinize the descriptions regarding parking so never had any surprises there.
A few years back I was booking cheaper rentals and my niggles mirror those of everyone above. I guess you get what you pay for? I always take with me a box of kitchen essentials including knives, salt, dishwashing bits, loo roll etc. It's a bonus when I don't have to unpack it. The linen not included seems to be a lot more common abroad.
The bad examples we've had (UK): 4 crap mismatched mugs, one of them so cracked I didn't want to use it, so we were constantly washing cups! That one also had a bunk bed where the bottom space was so low you could not sit on the bed. Probably because otherwise there would not have been enough headroom for the top bunk. Oh and a dubious sofa with a throw that kept slipping off. But the cottage was in a nice location...
But now our approach to holidaying has changed a bit and we spend a lot more time in the cottage so I choose with more care and attention to decor and comfort, not just location and price, and scrutinize all photos and reviews I can find.