If you're feeling fit, an ECE is an option.
For extra info, if the ECE was 400km or more, your overall time limit reduces from 12kph average to 10kph average. You'd still need to ride LEL within that event's time limit, but you'd effectively have more time for the ECE, as that plus LEL would then be 1900km+.
But I'm not sure you'd gain anything from doing the ECE versus a DIY. Same points. Marginally cheaper to do the DIY (£10 for 3 rides) vs the ECE (£4 for 1 ride).