Frank - digressing slightly, it's easier to reach STN from the Jewish areas of NW London than you might expect. National Express run a non-stop coach which originates in central London and runs from Golders Green to STN terminal every 15/20 mins during the day and every 30 mins at night. Coach takes about 55 mins from Golders Green to STN, while driving in a car takes about 45 mins.
Having said that, the fact that many of London's Jewish community live close to the train line between St Albans and West Hampstead does skew a Tel Aviv route in Luton's favour.