My husband and myself only started riding in May this year and I bought a second hand Raleigh Motus ebike with a 400Wh battery. My husband bought a new Kalkhoff Endeavour with a 600Wh battery. We did the Coast and Castles route in August and my battery nearly ran out one day after 45 miles but my husband's had quite a lot left "in the bank" so when we got home I sold my Raleigh and bought a Kalkhoff too. My advise to you would be to decide what sort of riding you want to do - if you think you might want to do long distances then make sure you get a bike with a 500Wh or bigger battery to give you the opportunity to go further without having to think about charging it mid day.
As mentioned above, try other local bike shops. We bought ours from Edinburgh Cycle Coop in Newcastle and got really good discounts plus other free goodies (bike locks, helmet, spare tubes to name a few).