Steve
  Is it a buyer is responsible for dismantling and removal from site? How will you remove the drive in one piece? 
 Only kidding
 
  A garage like that would cost £3000? to build - land £1000 and potential rent at £250 per year= £5000? + solicitors fees 
 My concern would be what is surrounding the garage. It looks like it's in the garden of a house. What happens if the house is sold and the purchaser is a thieving murderous drug dealer and turns the house into a brothel? 
 Could this be a potential disadvantage to owning the garage ( Or an asset? ) 
 Something to think about though. Also is it in a ' nice area ' or are you vulnerable to thieves who will know that you are not 'on the premises'. 
 Phil