The cherry picker can be good idea, but you need to check the following,
1. Can you get access to the area - i.e cherry pickers can be the size of a small car, and most at this site have to be pushed into position. Do you have the space to put the outriggers out - to set up.
2. Power, some are battery, diesel/petrol or can be run from the mains, the battery are OK as the charge should hold for a full days shift - as you only use power when the machine is being moved.
3. Price - check the min hire period, most show per day, then there is a min hire period and also a delivery charge and insurance.
4. Training - grey area, when the hire company hand over the machine they normally get you to sign two forms, 1st to say the machine has no damage when they delivered it (mark any damge/paint/scrapes etc as they will charge when m/c is returned) and 2nd they should give you a quick demo of the machine, what to do and what not to and what lever does what. - This form is a discalimer, passing responsability over to you.
Overall Cherry pickers are great, but there are so many out there you do need to check - some hire companies will offer a free site visit to tell you which m/c you should use.
If all else fails, get someone else to the whole job and tell them to use a cherry picker