Land Rover Certified program covers vehicle bumper to bumper from a warranty stand point, no wear items or maintenance (oil, filters, brakes... aren't covered obviously). Program covers the vehicle for up to 6 years or 100,000 miles from date of initial purchase (date when vehicle was purchased by first owner).
I purchased my first LR4 with it and was extremely happy to have it as it spent quite a bit of time in the shop. My second has it too and I already had to have some warranty work done.
I believe that by law you can do your own maintenance and still be covered by the warranty. Just keep your receipts and dates as well as mileage when the maintenance was performed.
LR uses a specific engine oil that you might want to comply with in order to make sure that they cover engine issues, however you'll find people on this forum using other oils and being totally satisfied with them.