I think you pays your money etc.
SE is better value
SEL is the better spec
Is the £3000 worth it? Probably not in terms of a 10-15% hike in the asking price.
BUT- The LED headlights are miles better than those on the SE
The car looks "nicer" with the chrome surrounds and inside improvements. Just feels a bit more classy imo.
The seats, a pain to clean maybe but they look smarter and you don't move as much
19" wheels fill the arches better (and still look a little small!).
If you keep the car for 10 years, are the above worth £300 a year? Only you can decide that.
Heated seats, keyless entry, power tailgate imo are next to worthless (others may disagree).