I would consider it - it is the nearest we would get to camping, as I would be put off by the thought of having to go wandering in the night for toilets.
I was looking at self catering in North Wales last week. We would need a family version as it would be two adults and a child. Since our daughter has been in school we have been going in August and have paid around £600-£700 per week for properties varying in size and facilities. Around £80 -£100 per night for the property would be within that range. I would consider paying more if it was something a bit different to the norm, or the location or facilities attracted me.
Most places we have stayed in have been bigger, but it would encourage us not to over pack 
I agree with having a space, outside if needed to store wet clothes/boots. Would help keep the property clean inside too.
A hot tub wouldn't really make much difference to us. Our daughter may like it, but I wouldn't pay extra. Having one or two onsite that could be booked ( even for a small charge) sounds like a middle road - less expense, less cleaning, but still an extra facility.
Having a number of businesses, pubs etc nearby sounds ideal as people may not be able to cook depending on what was in the little house, and others may not want too,
I possibly would pay extra if there was something such as a communal area, especially if family sized little houses were available. Not thinking club house, but maybe a room with a selection of family games etc, that there may not be space for in the little house but could give an escape if the weather was not good enough to be doing outdoor activities.
We have stayed in a number of places where the key was in a coded box outside. The last place we stayed in the owner was there to meet us but she only had to walk about 5 metres from the house next door.
If it helps. I usually start searching for holiday accommodation on the tourist board websites. I feel that way at least I know the website is a genuine provider. Searching might also give you an idea as to what else is out there and the prices being charged etc.
Depending on what else is nearby, if going to a specific attraction, I have also looked on their websites at properties nearby.