I have no idea what the prices are in the UK for Leafs, but what I did was get a used Leaf.
Pros: These are cheap used, since Leafs depreciate quickly. My 2013 SL had a new car MSRP of $39,000 and I got it three years later used for $9,000 or about 1/4 of the original price.
Cons: The older Leafs have smaller batteries. Also add to that that the battery is older and therefore has lost some of it's capacity, meaning I can't go very far in it.
If you go used I suggest avoiding the 2011 through early 2013 Leafs because the 2013 models are much better and the battery was improved substantially after April of 2013. The 2015 and "24kWh" 2016 Leafs supposedly have the best batteries for longevity. But newer used Leafs may have existing warranties that may be better than older models.
I don't think I'd recommend a 2017 Leaf at this point. The 2017 Leaf does have 25% more range than the older Leafs. But it will likely depreciate very quickly and not have as much range as the 2018. If you want or need a longer range electric car I'd suggest waiting for the 2018 Leaf. My guess is that it will cost about the same, be able to go farther and not depreciate as much as a 2017 Leaf. Plus the battery degradation is actually a bit worse in the 2017 Leafs than the 2013-2015 and 2016 "24kWh" Leafs.
2013 SL SOLD
1972 VW Beetle SOLD
1984 VW Golf diesel CURRENT
2013 Toyota Avalon Hybrid CONTEMPLATING