Unmarried Partner visa Please help!!!!!!

Hi

I am a South African currently living in Ireland on a work authorisation visa with my Partner who has an Irish passport. In March next year we plan on heading to South America for 8 months of travel. Following our travels we would like to go to the UK to work. My question is it possible to apply for the unmarried partner visa before I go traveling or during my travels and then only use it when I finish traveling, so that I don't have to waste anytime when we are finished traveling to head to the UK to work? Can some please also tell me what sort of documentation you require to apply for the umarried partner visa.

Any help will be much appreciated!