The first;
There are 2 examples of that exact make model derivative nationally, on a 59 and 10 plate (I always search one plate newer especially on low mileage stuff) and you are number 1 from 3 in terms of value for money. Rono Prestige has had his Teal blue one in for 72 days and has just reduced it in price by £500 today. If you expand this search to similar derivatives (this now includes the SE spec) then the results are the same. It's clear you are in pole position for anyone wanting that make/model/derivative around that mileage with that sort of budget. Rono Prestige have overpriced theirs possibly, especially given the hideous colour.
The second;
Because of the low mileage, I capped the search on this at 25,000 miles, just above yours.
Nationally, there are 17 of these examples, 64 or 15 plate, up to 25,000 miles.
Within a 50 mile radius, there are 9 examples. You are 8/9 in terms of value for money, with your other I3 coming in at number 7/9 in terms of value for money. Frosts of Brighton are at the bottom however they are seemingly overpriced and it shows by virtue of the fact they have had their white one in for 287 days, making 2 price cuts in that time, the latest on the 12th July. Of those 6 dealers that are above you and Frosts, they have held these vehicles for 127 days, 68 days, 15 days, 11 days, 11 days, 35 days. I look at that make/model/derivative as something of a competitive department and quite a few of them within your area. If it were me, I wouldn't see there to be a shortfall in that area. That said, there are a good number of low days held in that, 15, 11, 11 and even 35 days. So perhaps these cars do turn quickly but there is definitely plenty of choice around a 50 mile radius of you.