Britain is on top of the world in Formula One, with Lewis Hamilton beginning his quest for a fifth championship in Australia this weekend, but there is concern at grassroots level. With costs spiralling and some junior kart teams racing on six figure budgets, youngsters hoping to emulate Hamiltons rise from social housing to stardom are being priced out of contention. Britains Motor Sports Association says the number of MSA licence holders in karting — where future champions learn their craft — has fallen by 30 percent in the decade since Hamilton made his grand prix debut in 2007. Less than 12 percent of the total are under the age of 21.