SING FOR YOUR SUPPER by Pamela Frankau. 311 pages. Random House. $4.95.
Sherry is the drink Pamela Frankau is offering here for those who take itout of a cut-glass decanter, and perhaps a biscuit to go with it. The time is 1926, when England was just recovering from the general strike. Back from assorted boarding schools, the three Weston children are assembled at a seaside resort where Daddy's musical show, The Moonrakers, is definitely not raking in the cash. Mummy has been dead for years, and Daddy has contrived a living out of a shoestring and the old school tie (Eton) by...