You mentioned that your are flying in 12 days time, so I took the liberty to do a dummy booking GLA/DXB on 9 October (as part of a return on 23 October but the date of the return is immaterial here, as long as there is a return date).
On that date there is Flex availability at £3681 (per person, my dummy booking is for 1). Flex+ is £4500. If you are currently on the lowest J fare (Saver), which is £1715, the difference multiplied by 4 is just under £8K. So unless you get a special offer (by email, usually a few days before departure), I am afraid this is as good (or bad) as it is. The chances of getting such an email for 4 people are not good (but not zero).
Unfortunately, flying to DXB is expensive and especially in First class. Comparison: a few weeks ago I upgraded LGW/DXB/CPT fro J saver to F Flex for just under £800...

If you can confirm that you are due to fly 9 October, I can check the seat map. That is not the most reliable way to check availability, but I am currently just using a free ExpertFlyer account which gives me limited availability to seat maps but noting for availability.