Hiya
I am now getting all the arrangements in place for the log cabin.
First thing I would do would be speaking to your council. I know that in 99% cases it's very straight forward but you should see my face when I found out that although my cabin would be the right dimensions etc I live in the area where the permitted development rights has been removed and I need a planning permission which costed me £430 incl. technical drawings and architect and delayed me for 8 weeks!
Make sure first your council won't surprise you
and if you want water and electricity connected, couple of sockets, concrete foundations (much better than pads etc,) and cabin erected, make sure you have at least £3000 up to £4000 on top of the cabin price. And that's for the cabin 3mx5m which is about 10m away from home.
Obviously if you have a builder or know someone who can do it for you it will be much cheaper. I am not that lucky. But you still need a building inspector around if plugging electricity and water so no cutting corners on this.
Overall don't just look at the price of the cabin but also workmanship, vanity sinks, heating, aircon etc.
I am writing this to warn you
I was naive enough to think that £6000 budget will be more then enough...no one told me what the reality is xxx
Good luck xxx