you would need an IPAF pass for the cherry picker. the pass will last for 5 years and cost about £200. for the 200 you get a 6 hour course, a multiple choice test, a practicle test and a photo pass. if you are unlikely to use a cherry picker on a regular basis it would not be worth the cost. not sure about the cost of a hire but it'd probably be less expensive to pull the old gutter off and replace it than do the course, hire the cherry picker and then clean the gutter.