You can fit a universal charger which doesn't come with a lead, meaning you can plug pretty much any electric car into it. The downside of this is you'll have to take the lead out of the boot and plug it in every time you use it, but at least the charger should be future-proof. Alternatively, fit a tethered unit with a Type 1 or Type 2 lead already fitted. Most electric cars are charged using either Type 1 or Type 2 charging leads, with Type 2 expected to become standard across all EVs, although some cars (including the Nissan Leaf) still use the Type 1 connector. If you opt for a tethered unit with one of these leads, it's not a huge job for an electrician to change it in the future. Alternatively you can buy an adapter for around £100.