Looking for self contained space

Looking for a self contained area - something like an annex or garden house. I work from home for a software group so shared housing is a struggle.

Please no agencies - live in landlords only. I have rented though spare room before and had good experiences - last time I rented a loft space with an en-suite and was able to work and live up there. Just to give an example of what I am looking for.

I do work away a fair amount so I won't always be around. I gym, play tennis and football most mornings and evenings so I would like to say that with working away, the wear and tear on any space I stay in would be low.

I am in a position to buy a house but the market is dead and I don't want to buy something for the hell of it. Looking for somewhere I can look and buy when I am ready.

I don't drink alcohol so you won't experience an fool coming home and making noise and stupid hours.