In the UK all new dwelling houses need either planning permission or building consent so this would be your first task even before looking or building your log house you will also need to make sure that any building plot you buy would be suitable for this type of dwelling and that you could get planning permission for a log building to be erected on that plot. If the plot of land already has some outline planning permission you must make sure what kind of dwelling is stipulated on the planning consent as you may have to reapply. Some outline planning permission does not state the type of dwelling that can be constructed where others do, so it is vitally important that you get this sorted out before purchasing the land that your new log house is going to be erected on. Once you have planning permission or building consent in place the next task will be looking for the right log house to suit your needs and what you may need to have in place such as a concrete foundation for your home to be placed upon along with any amenities that are going to be needed.
For more information on planning and building permission go to the government website.