Take the M23 to Brighton and follow the A27 through to the A259 to Pevensey Bay. The Pevensey Bay Beach House is an hour and 10 minutes from the M25 / M23 junction.
1066 country is well service by a number of alternative routes including the A22 via East Grinstead and the A26 from Royal Tunbridge Wells.
Southwest Trains run a regular service from London Victoria via Clapham Junction to Eastbourne and on into Pevensey Bay. Travel time to Eastbourne is circa 1 hour 30 minutes.
Trains also run from Brighton through Lewes and into Pevensey Bay.
The nearest airport is Gatwick that is an hour by road to the house.
Newhaven is a 30-minute drive away with a regular ferry service to and from Dieppe.