I haven't stayed in this type of accommodation for a few years now. However we often did when the kids were younger. When you are self catering (for a wide variety of reasons) and often rurally, the last thing you need is the host to have skimped on the kitchen essentials.
Make life easier for your guests: washing up liquid, dishwasher tablets, a few washing machine tablets/powder, sponge, dishcloth, tea towel etc soap, some surface cleaner, loo cleaner, bleach, bin bags. Basic store cupboard: salt, pepper, herbs, some oil, teabags/coffee. The list could go on.
I'm not saying branded everything - Aldi&Lidl rule - and I'm not saying leave a full box/bottle that you're worried will be taken back by your guests. If you are charging £100-£200+ per night then I'm sure that can stretch to some basics that guests don't need to either bring with them or purchase unnecessarily while there perhaps going out of their way to do so.