For the squid. Rinse the squid thoroughly and shake dry. Cut each squid body down one side so that it opens out flat. Use a small, very sharp knife to score the flesh on one side in a criss-cross pattern, taking care not to cut all the way through.
Place the scored squid bodies and the tentacles into a bowl. Add the thyme and olive oil mixture, mix well and set aside to marinate for at least half an hour.
For the dressing, place the lime juice, olive oil and thyme leaves into a clean screw-top jar. Screw the lid on tightly then shake the jar vigorously to mix the dressing.
Heat a griddle pan over a high heat until smoking. Add the squid and griddle for 30 seconds on both sides (the squid bodies will probably curl up during cooking) or until just cooked through and lightly charred in places. Take care not to overcook the squid.
To serve, divide the squid between two serving plates, pour over the dressing and season, to taste, with flakes of sea salt. Serve at once.