I would agree that this is a nice route but beachy head road towards birling gap is now pretty poor condition, very bumpy with many pot holes.... Nice route but take care!!!
Short 20 - 30 minute run, assuming you are not in a hurry and you don't stop. Starting from the pier in Eastbourne and ending at East Dean where you can join the A259 and either go on to Seaford or back to Eastbourne. It is worth stopping at Beachy Head otherwise you miss the views across Beachy Head, the famous cliff that rises 162 metres (530 feet) above the sea below and is the highest chalk sea cliff in Britain. After walking about and/or visiting the pub at Beachy Head, you can continue the trip and enjoy a run down the scenic Birling Gap. You will also see a few of the sisters that make up the famous Seven Sisters Cliffs. All to short unfortunately but well worth a detour if you are in the area.