Long Haul FO increment is just under £3000 per year.
Commuting no problem on the 380. Of the daily departures there are 3 FO slots on 3 day trips (will be 5 for part of summer), 6 on 4 day, and 6 on 5 day. So the majority of trips are longish, most get back early, none too late for flights to France, and only 1 of the reports (2 in summer) isn't commutable from France on the same day.
You aren't tied to A380 for upgrade, but, it will be long time if you don't want to fly another type. A350 may be less, and A320 certainly much much sooner.