In reply to Chris Fletcher-Smith BRM June2020. Howard raises many good points. I have used a portacabin very successfully. Points to bear in mind are that included in the price is a strong insulated floor. It will probably come with a consumer unit, several double sockets, lights and electric convector heaters. Apart from connecting to the power it is ready to use as soon as it is delivered. Mine came with a small sink unit and water heater.
Preparation requires the provision of four good strong pads of concrete for the legs to rest on. A farm jack is a useful accessory for leveling the cabin and removing twist. If you were contemplating building a shed focus on adding a pent type pitched roof with additional insulation. You can then overcome any potential leaks. Check all outside seals and give it a coat of paint. John