Registration the day before, innit. Would save me ££££ that's all.
ECE it to a long enough distance to bring the speed right down - 10km/h overall if you go for 1900+km, 200km/day if you go for 2500+km IIRC.
Indeed, this can work out really well if you front loaded LEL:-
Ride 500km to the start giving a ride length of 1900km (we'll ignore the overdistance bit of LEL...). As John says, this drops the average speed requirement down to 10kph overall (for rides of 1900 to 2499 km).
Overall time limit = 1900km / 10kph = 190h.
Take off the 116h40m for LEL and that leaves you 73h20m (3d 1h 20m) to do that 500km to the start.
If you got a morning LEL start (say 10.30am) that would mean you could start your 500km ride on the Thursday at 9.10am.
You should be able to knock out two 250km days with plenty of sleep meaning you'd arrive at the start on Friday evening (or Saturday morning if you took it a bit easier) in plenty of time to register, drop off drop-bags, etc. You could then have this rest day before starting LEL on the Sunday in your allotted start group.
That solves both registration and drop-bags problems. If you didn't want to carry your drop bags on the 500km section of the ride you could just arrange for someone else to take them to the start for you, and you'd be there on the Saturday to hand them over.