Summerhouse blues

I have a limited company client owned by a husband and wife. The company trades from the main residence of the husband and wife using two of the spare bedrooms. The husband and wife wish to move the company out of the spare bedrooms and into a large summerhouse at the bottom of the garden to be purpose-built for the business so that staff may be employed.
Is it possible for the company to own the summerhouse thereby reclaiming the VAT on the construction costs? In that event I am assuming that the company would rent the piece of land from the husband and wife on which it would build the summerhouse. Would the husband and wife then be subject to capital gains tax when they sell the main residence? Alternatively as the summerhouse is owned by the company would the company have to pay...