The day at the seaside is a living British tradition celebrated by millions of city dwellers every year on cheerful expeditions to resorts all round the coast, from Brighton to Scarborough, from Bournemouth to Rothesay. The name in the lettered rock changes from one place to another, but the flavour is the same. Jack Pizzey , and a Man Alive team, have been at Margate observing that British institution - the Day Trip. For the family with kids -the youngest hadn' seen the sea before - it's the beach; for the pensioners it's the pub. the deckchair and the memories; for the teenage working girls it's bars, discos and big-dippers.