I would like to find as much history as I can about a particular
house. When was it constructed, who by, who for, what has it been used
for, who lived there etc. The house is called Etonhurst and is in
Ashcott, a small village just outside the town of Street in Somerset
in the United Kingdom.

Most recently, it has been a boys boarding house for the nearby school
of Millfield. I believe that in the past, it has been a nursing home
amongst many other things.

Dear msc77-ga, 
I do not know where in the world you are located, but a good place to
start, would be a visit to the Somerset Archive and Record Office.
There you will be able to look at the census returns, tithe and estate
maps, parish records, and with luck, some records relating to the
property you are interested in such as deeds and rate books.
For instance, go to their web site.
http://www.somerset.gov.uk/archives/
Click on the Online Catalogue
Click Search Catalogue
Enter> Etonhurst in the Any Text field, and you will see they have
some records on the school.
Enter> Ashcott in the Any Text field, and you will see 344 records
relating to that parish. Some these will no doubt contain information
on the property, or the people who lived in the house.
From the Home Page click on Maps and Pictures to view the Ordnance
Survey maps for the area.

If you cannot visit the Record Office yourself, most offices have a
list of Professional Researchers who can conduct the research for you.

Hope this helps.
answerfinder-ga
Google Answers Researcher (and experienced house history researcher)

You could do a search at the Land Registry.

Their number's in the book & the folks there are very friendly.

There would be a small charge (about £20, I think) if you order up the documents.

Thanks for both your comments, they are very helpful and I will action them!
msc77-ga