The boat in the link looks like quite a good boat, but it needs radio gear and an esc (speed control is what esc stands for)
so you would have to allow for that plus batterys and charger.
yes the frequency is diffrent in the uk but as long as your not racing it doesnt matter you just need to make sure the transmitter, x'tals and receiver are all matched to the same frequency.
As for run time that all depends on the quality of the packs and how much your willing to spend on them. Without dought lipo power
is the way to go for run time and power.