Plenty of CL on way but as its August they may not do one night stops and will get booked up.
Do you have to travel Friday night? Presumably its to miss the traffic.
We go to Cornwall every August for last 10 years. For last 8 we have left home 4.00am (ish) on saturday morning, stop at Exeter for breakfast (either service station or tesco store) and get to Cornwall site at around check in time. get the caravan set up and off to beach or attraction by lunchtime. If the pitch has not yet been vacated, we leave the caravan in the site car park and go off, get back late afternoon and set it up then.
We usually put the car on the road the night before with caravan locked onto back and everything packed, my hubby makes some sandwiches, drinks and snacks whilst I go to bed around 9pm. get up around 3.30am, used to carry the kids to the car still in pyjamas and asleep but now they are older and wake up and get dressed. I drive and most times everyone else is asleep again within 10 minutes. When we stop at Exeter they jump in the caravan and get dressed, clean teeth. My children now 17, 15 and 9 so more likely to be awake now, but its easy to do and you get an extra day's useable holiday for your money.
hope that helps
Wendy