On Tuesdays and Thursdays, Go-Ahead London operate a return trip, numbered 773, to Brighton from Dorking (school days) or Sutton (school holidays).
SCHOOL DAYS
K2: 0656 Berrylands to Hook (0713)
465: 0733 Hook to Dorking (0829)
773: 0840 Dorking to Brighton (1020)
(Three hours in Brighton)
773: 1330 Brighton to Dorking (1510)
465: 1535 Dorking to Hook (1637)
K2: 1648 Hook to Berrylands (1708)
SCHOOL HOLIDAYS
K2: 0709 Berrylands to Kingston (0728)
X26: 0737 Kingston to Sutton (0818)
773: 0830 Sutton to Brighton (1020)
(Six hours in Brighton)
773: 1630 Brighton to Sutton (1830)
X26: 1833 Sutton to Kingston (1908)
K2: 1917 Kingston to Berrylands (1931)
Alternatively, they also operate a more limited route 775 from Kingston to Brighton, then on to Eastbourne. It operates Sundays/Holidays 26/29 May, 2/9/16/23/30 June, and 7/14 July.
K2: 0807 Berrylands to Kingston (0821)
775: 0845 Kingston to Brighton (1100
(Seven hours in Brighton)
775: 1815 Brighton to Kingston (2030)
K2: 2043 Kingston to Berrylands (2054)
The downside is the 773/775 both require payment - £10 return. No concessions.