The Brew Cabin

I am about to purchase a 2 storey playhouse (10' x6') for my son, and i would like advice on what type of base would be most suitable.
The area were i am hoping to place it, has very poor drainage due to a natural spring at the top of the street, which then seems to collect in my garden.
I am trying to steer away from a concrete base as then the water would find somewhere else in the garden.
So would a raised timber frame be suitable ?

I'd go for reclaimed flags - old 2x2s or 3x2s laid on a simple bed of grit sand, and then erect the playhouse on wooden baulks sat on top of the flagging.

This gives a firm and stable base that is weed free and unattractive to vermin, while providinga dry base for the timber baulks which lift the Playhouse above ground level and so keep it away from all that nasty damp.