1. Only people I'm aware of hiring gutter vacs is omnipole, I think they deliver for a fee.
2. Gutters will only be full of water if they are totally blocked, once you've cleared the blockage the water will drain along the gutter. My vac is fitted with a pump to pump liquid out, which I presume is the same for ones you buy/hire. TBH I have removed the pump as find it's not required. My vax is similar to omnivacs but with only 2 x 1200w motors, but find this adequate for domestics. I bought the poles from omnivac 36', quite heavy to use and difficult to control at anything above 24'. I tend to use a combination of gutter sucker (it's a wet and dry vac, not allowed to call it a "guttervac"); pressure washer with extending lance and gutter attachment, and a scraper attached to the end of a harris pole.
I'm in Shrewsbury, if you ever get over this way, be happy to show you my kit.
Neil