I think it is fair to say the UK’s best landscape competition is the Take-A-View Landscape Photographer of the Year Competition. The 2012 competition is now open and you have until midnight on the 15th July to enter up to 25 photographs. There are cash prizes, a London exhibition and the winning shots are published in a hard back book, so well worth having a go.
If your work is a little more Contemporary, you might fancy entering FOTO8′s Summershow competition. It’s being judged by photographer/artists Simon Roberts, Gerry Badger, Alison Jackson and BBC’s Phil Coomes. The winners can exhibit and sell their prints in the London gallery show. Have a look at the previous years entries. The deadline has been extended until the 15th May.