Many 1000w motors are ungeared and good at speed but not good at hill climbing. A 1000w motor will not be legal as a pedelec regardless of any speed restrictions put on it.
A good quality legal 250w motor actually peaks well over 250w and should get you up most hills. Depending on weight and how hilly you will probably be best off with a crank drive one and fairly low gears so the motor can keep its optimum speed even when the bike goes relatively slowly on hills. For reasonable prices look at the Woosh range (
http://wooshbikes.co.uk/), and if you contact them by phone and email they will give good advice. They aren't trying to get sales that lead to unsatisfied customers. If you can afford more Cube are pretty good, or other Bosch powered bikes.