OK there’s a bit of a bottle neck at Hythe, I experienced it myself last night a ten minute journey home took 45 minutes but there is a route you can take.
So A27 to Other side of Eastbourne, then head inland toward Battle to miss Bexhill & Hastings you use the backroads through villages Hooe, Ninfield Catsfield, pick up the A21 then head back toward hastings, then left A28 to Broad Oak then right through Udimore into the back end of Rye, then you have a choice of the A259 which is a bit touristy this time of year or there are back roads across the Marsh through Appledore, Snargate, Newchurch, Burmarsh, into West Hythe, you can then go Lympne pick up the A20 at New Inn green and you are then in the mix for the chunnel traffic.
That will work becuase not many folk know it other than us frequent south coast travellers in tourist season it’s also a good road bike route with little traffic. Map it out first. Don’t get suckered onto the M20 or they’ll route you round in circles, best come into Folkestone then head back out to the Tunnel entrance that way you’ll get right into the pipe.
Good Luck I can see them moving a bit now but there are five thousand trucks to clear and it took almost a week last time.