The situation is a farce - I catch the 0831 Redhill to Victoria some mornings, which originates from Horsham. It is usually a 377/7. The first class even within this small sub-class varies hugely - at least one unit (377704) has no first class labeling at all, and others have varying amounts labeled. The actual labels are positioned on the windows such that they are almost hidden by the seating, and the headrest cotton covers that are supposed to be applied when operating in first class mode are almost always missing (and are pathetic little bibs that fall off anyway). Passengers clearly have no idea what to make of it, and the conductors I have spoken to think it's a shambles. The 377/7s have different first class layouts to the 377/6s, which are both different again to the rest of the 377s (some of which have glass doors and some don't).
The whole thing smacks of very poor stock design planning at the very least, and has resulted in a situation where no-one benefits - first class ticket holders who pay extra are invaded by unsuspecting or uncaring standard class ticket holders (the latter knowing they are very unlikely to be challenged and who probably think a £20 fine once or twice a year is very good value for first class travel!), while genuinely-mistaken passengers risk fines. The use of identical seating in both classes leads to further confusion (especially with Gatwick passengers) and, of course, the seating in the 377/6s and 7s is so poor that most people don't regard it as adequate for standard class, let alone first! Connex did attempt to abolish first with the original specifications for the fleet, but were forced to abandon that by vociferous commuters, and Southern have had opportunities to rectify the situation since (not least with the refurbishment programme) but have failed to do so.
) but in the picture supplied by the OP first class branding is visible in every shot. 
