You haven't said what year/model but recent Classics have blue/yellow cables tucked away under each front wing with connector to optional switch behind dash. This switch takes its feed from BCU if your car has one, which inhibits power to lamps unless headlights are on.
Ground connection for lamps you can pick up locally. Look for or provide double female bullet connector fed by black wire.
Note there may be two blue/yellow cables under r/h wing one providing power and the other looping across to l/h hand side. The wiring diagram suggests these two need to be joined together, typically with double female bullet so you have power to both sides. This may have already been done by factory.
