OLCI opens at T-24 or there about, usually at 23hrs 59mins before your flight, never seen it open before this.
As long as you complete OLCI 2 hours before it closes you should get your assigned seats....
should being the operative word given the myriad of reasons VS could change seating requests at the airport ii)
At LGW you get to use the priority security queue.... the check in desk can direct you where to go, but to be honest the security system at Gatwick is quite efficient and sometimes it is quicker to use the normal one as opposed to the priority lane. I would say, judge it on the day by how fast things are moving.
On your marks, get set... GO
