summerhouse - build or buy?

[PE]

Hi
Looking at a 18 ft wide by 12ft deep summerhouse for redesigned garden.
Any opinions on whether the price differential would be significant on a DIY building as opposed to purchasing an off the shelf building.

Items I've looked at include the Diamond Wilbye range of summerhouse and seem to be about £3k for this size built and erected (plus cost of concrete base)

Thanks

 

[WabbitPoo]

Cost wise, I imagine (though I have never costed one) that raw materials will be cheaper than the whole. After all, you time is free, right? That said, how competent are you? No point in saving a grand only for the boss to take one look at it and hate it........