The Haibike pictured above is a great piece of kit. They come in Sduro (Yamaha powered) and Xduro (Bosch powered) models. The Yamaha units are less pricey and some prefer the way they work over the Bosch.Raleigh, whom supplies Haibike, has a range of their own ebikes as well.
Freego have a great line of bikes as well with very good warranty. Their well equipped Hawk is £999. They have upgraded the Eagle this year and it is great spec for the price.
Buying the most inexpensive ebike you can find is just that, an inexpensive ebike. Having said that, regardless of what you buy, if you take good care of your bike and have a dealer that will take care of you, you should be okay.
Bottom line is visiting a dealer or dealers and test riding a variety of bikes. Anyone here will tell you that a volume of words can not replace a five minute test ride when describing the ebike experience. Good luck with your purchase