The best thing to do is to stay in the cottage as a guest yourself, or have some friends who you can trust to be objective.
Decent set of knives-we've learnt over the years (and we've holiday cottaged for 15 yrs, so we're quite well seasoned cottagers) to take a knife sharpener with us, or at least provide a REALLY good sharpener.
Allow dogs, most places we've stayed at charge anything up to £20 pr wk EXTRA for a dog-ouch!!
Loads of piccys in the brochure/website.
A welcome tray with local produce is nice, one cottage in Coniston (lakes) we stayed at provided bottle of wine, but nothing else, I prefer the welcome tray-tea, coffee, home cooked cake etc....
Recipe folder.
The cottage we stay at every year in keswick leaves a note with a 1-10 scale, how clean was the cottage type of questions, any additional comments.
Visitors book, and maybe a book for recommendations of local places to eat/drink, that both you, previous owner of the property & prev holidayers have eaten. This is another recommendation for yourself- eat at the local places so you can personally say you've been and would/wouldn't recommend.
My parents have a B&B and have done the above. (not the recipe folder obviously!!)
Cling film/foil.
Decent size pans, roasting dishes etc...
HTH.