BEFORE her death in 1976, Queen of Crime Agatha Christie described Joan Hickson as the ideal actress to play her ageing supersleuth Miss Marple. That's a pretty good recommendation for tonight's final BBC Week offering, a Christie mystery which stars the said Ms Hickson as the said very private detective. Agatha Christie's Miss Marple: They Do It With Mirrors (Pearl, 9.45pm, Original Running Time 111 minutes) revolves around a murder at a country mansion. The problem is Miss Marple knows whodunit, but not how they dunit. Miss Marple is summoned to Stonygates mansion by a friend worried about the health of her sister Carrie-Louise Serrocold, played by veteran Hollywood actress Jean Simmons (Guys and Dolls). Our intrepid spinster finds the sister in perfect health, and she's more concerned about the obvious trouble brewing among other members of the feuding family. Husband Lewis Serrocold (Joss Ackland) is a social reformer who's making powerful enemies, and the woman's daughter and grand-daughter are constantly fighting among themselves - when they're not dosing granny up . WORLD'S alternative is a disaster movie in more ways than one. The Concorde - Airport '79 (9.30pm, ORT 123 mins) is the last in the Alex Hailey-inspired quartet of air crash movies. The film employs the usual smattering of past-their-sell-by-date stars - Alain Delon, Robert Wagner, Sylvia Kristel, etc - whose presence is somehow meant to get the limping plot off the ground. They're passengers on a goodwill Concorde flight from Washington to Moscow to celebrate the 1980 Olympics (irony, irony), but unbeknown to them all, there's an arms dealer on board. Concorde manages to stay airborne, but that's more than can be said for the film. HALLELUJAH! Only twentysomething installments into the 153-episode - yes, that's 153 - Japanese cartoon series Dragon Ball (Pearl, 12.20am) and Pearl has taken the breakthrough initiative of adding English subtitles to the Cantonese ones already available. Be careful you don't get trampled in the stampede home from the pub tonight to watch it. HONGKONG Nuclear Investment Company is making another two-minute attempt to sell us on the advantages of uranium as a fuel in Nuclear Safety (Pearl 8pm, World 8.30pm). Both terrestrial channels have been showing this mini-series of mini programmes, whose purpose seems to be to reassure Hongkongers that when the Daya Bay nuclear power plant comes on-line this autumn it won't be necessary to keep a stand-by ticket out ofKai Tak constantly on our persons. What is odd about the programmes is their advert-style format - uranium is being touted as though it were a nice new car. Daya Bay is being built, it's too late to start selling the idea now.