I remember in the days of British Rail two summer Saturday or Sunday Intercity Crosscountry services from somewhere north of Birmingham that ran to Eastbourne and Dover Priory in the 1980s/1990s if my mind is not playing tricks on me.
I seem to remember some of the seaside resort summer weekend services going south from Birmingham called at Birmingham International, Coventry, Milton Keynes (or Watford Junction), Kensington Olympia, East Croydon?, Redhill, then either Gatwick Airport, Haywards Heath, and Brighton or Eastborne, or to Dover Priory via Tonbridge, Ashford, and Folkstone Central.
There was a traction change (most likely at either Wembley or Willesden) as BR had a strict policy of no diesel traction being allowed under the wires.
In the last couple of years of BR, these services were rerouted between Coventry and Kensington Olympia to run via Banbury, Oxford, Didcot Parkway, and Reading. These journeys may have been run by the Intercity 125 HST or loco hauled coaching stock with a change of traction power at Birmingham.
In peace
Adam