It is considered permitted developement to have a mobile, park home, Lodge, Log Cabin or Annexe in your garden upto 6.8m x 20m, although dependent on where, so long as it is on a base that can be moved at anytime i.e. on a metal chassis with wheels on similar to that of a static caravan. It is not permitted to be self-contained though. For example you could sleep, live and cook in it but not eat your meals in it, you will have to use the main residence. You will also need to spur off the main residence's utilities with no seperate meters and also have a connection family or friend wise with the main residence occupiers. If you wish to have it sited on a chassis or permanently on brick pillars or a concrete base and have it self-contained you will require planning permission, but this should not be to hard to obtain as long as you do not reside in a conservation area, your home is not listed, the land is not Arable or covered by a covenant. For more information on this and other planning issues please visit the following website: www.planningportal.gov.uk This page is for guidance only. You should seek advice from your Local Authority regarding planning laws in your area.