Right, I have just checked in for BRS-EDI next week. Truth is, I left it a bit too late because I was allocated seat 18B. There now seems to be no way to change it, once checked in. I also ended up buying a GBP10 inflight catering voucher for GBP8. I reckon the trick with this is to check in as early as possible.

And it wasn't a particularly good flight experience. First, I had to put my rucksack into the sizer. Fit without problem, but it wasn't good enough - it had to go in sideways, which it did. So, all was ok but the whole process irritated me, it felt like a scam cash grab and made me grateful that I'm not a regular easyJet traveller. The cabin crew weren't particularly great either, offhand and borderline unfriendly. You can't have a great flight every time, given the number of flights I've done, so that's fair enough. I had a catering voucher to use and I was stuck behind the trolley all the way down to row 18 after a visit to the toilet. They could have let me pass when we were at the top of the cabin but they just didn't care. Won't buy a catering voucher again and will just keep my money to myself.

Just another data-point: on a flight BSL - HAM I checked in 21 days before departure, on a ticket (single ticket, no speedy boarding, no luggage). Seat map showed a plane that was approx 60% empty. front part was well filled, and the back half was completely empty. I took a gamble....
.... and got a "B" seat in row 21. grrr...
It's a short flight, so not too tragic, but also not fun. I'm tall. I think I should have waited until closer to flight date. Learned my lesson.

I thought that the earlier you checked in the more likely it was that you would receive a better seat. I recall it being the opposite with Ryanair, where if you checked in at the last minute you were almost guaranteed a good seat.

Last three EZY flights, all checked in about a week before travel, all allocated an F seat and one of these was the exit row.

As I was travelling alone in all three cases I didn’t care where it was in terms of aisle or window or front or back, but if it was a middle I probably wouldn’t have been too happy. The flights are so short that I don’t think I care enough to pay.

it has dispelled the myth in my head that they allocate middle seats to upsell paid seating etc. Maybe other airlines like Ryanair do this though? No idea.

I travel regularly with Easyjet, on average !'d say once a week. Most of my travel is alone and with hardly any luggage, so I usually purchase the cheapest ticket possible with no options such as an allocated seat. I'd say, based on my N=1 experience, in the past 100+ flights, there is no strategy to minimise my chance for a middle seat. On my routes, I usually have a 80-85% chance landing an aisle or window seat. Late or early check in does not seem to make a difference. The algorithm seems random to me.

EasyJet will, in my experience, seat people on the same booking together. So, unlike with Ryanair who "randomly" split groups up across all 27 rows of the aircraft, with EasyJet there will be fewer unoccupied middle seats to allocate. Couples will be given aisle or window + middle so single travellers are much more likely to be given an aisle or window.

Not sure if it’s actually allowed but I just wait at the back of the queue and then take my pick of the empty seats once on board…

Me too - bit of a gamble sometimes but much less fuss than moving from one seat to another once you're on the plane!