Summerhouse roof drainage

[Jimmy3]

I have a largish summerhouse at the bottom of my garden.
I haven't got a photo of it as yet but it has an apex roof and is similar in design to this:
http://www.northstreetsheds.co.uk/standard-summer-house
It is 6M wide by 3M deep.
Up until now it has been used as a glorified shed but i want to insulate it and get some use out of it as an additional room.
The first part of this project is to stop it getting damp.
It doesn't have a gutter on either side of the apex and when it rains water drips off the roof and runs down the shiplap cladding in places or bounces off the floor onto the base of it.
My thinking was to install gutter along the two 3M sides and then collect it into 2 separate water butts or somehow connect the two gutters into one (along the back) and then into one 200l butt.
Does this sound like a good idea or should the gutter be connected to a proper drain?

 

[terrypin]

That's a sound idea or you could make a soakaway though more hassle but you wouldn't have to drain it when full.

 

[Mw Roofline]

Overhang each gutter to the back by about 8 inches then offset long pipes from each into one butt

 

[Jimmy3]

Thanks for the advice.
I'm going to have to locate the water butt towards the front and away from the Summerhouse as there is only about 60cm clearance around the back as it is sited close to our neighbours wall.
Also as the butt is likely to overflow on the winter (as i don't have access to a drain) it will need to be approximately 4M away from the front as there is 3M of decking to the front as well.
Does connecting the 2 x 3M runs of gutter (at the bottom of each apex) with a 6M run along the back of the summer house (i.e. out of view) sound OK?
I was then going to fit a stop end outlet on one side and then run approx 4M in downpipe to the water butt.

 

[Mw Roofline]

Yeah sounds about right as long as it doesn't look shyte.