Jesus this thread has turned into some ****show that's not really giving the OP any constructive advice.
For your info OP, I built a log cabin out my back garden ten years ago, initially just for my teenage lads to play music but it always had a shower and toilet in case we wanted to use it for long term use.
Turned out my daughter lived in it for five years. It is the warmest, cosiest space I've ever been in. With one electric storage heater that only had to be on for an hour a day it was always warm and cosy.
I would live in it now myself except it's in Dublin and I don't want to be there anymore.
May change my mind as I get older though and it's still available for me.
No planning permission was granted but then again none of my neighbours ever complained.