Small Garden Room / Shed Design 2D CAD with measurements

I need a design from scratch for a small garden room, internal dimensions need to be 6m (length) x 3m (Width). The building will be made from blocks and then rendered. Ideally a double door on the front, a window at each end. One end needs to be for storage for things like a lawnmower and general tools etc. The main body of the garden room needs to incorporate a running machine (190cm x 90cm) spinning bike and free weights. Upon one of the 6m walls there doesn't need to be any windows as it backs onto a fence. The roof is to be a flat roof sloping towards the fence with a gutter on it leading to a center downpipe.

Roof height must be a maximum of 2.5m as I would like to fall under permitted development.

If you could please include past work with the proposal. Also, automatic proposals will be ignored.