warm welcome, i love Wales especially North of Bala Lake.
think some initial pointers would be wise here for such a hilly region.
these machines are a bit delicate in the transmission department, they don't like going up steep inclines let alone hills, and can be a white knuckle experience on the decent due to what is laughingly called the brakes
.
Front wheel is plastic and fun when it gets hot, melts and sheds the tyre, rear brake is a drum design only acts on the 'off' side, tends to cause severe twitching and a need for underpants change in the wet.
as said the original battery will likely be dead, this site sell a leisure conversion kit and i'd say the 1st thing to do, you can then use a standard car battery.
the expensive to replace electronics are also protected against accidental battery reversal, have quick release post clamps, top bit of kit.
not wise to wheel it backwards muh as the motor acts like a dynamo and feeds current backwards into the controller, which can damage it.
i'd recommend swap out the brake blocks for what they cost, as they are by know hard as cement likely cause extra damage to the front wheel rim.
last but no least lubricate all he bearings, not much was put in at the factory and what is there has possibly deteriorated, plenty of manuals and how to in the forum.
good luck
Alan