Leisure group Whitbread said it has started the new financial year well, as strong growth at its Costa and Premier Inn brands made up for weakness in the restaurants division.Total sales increased by 12.5% in the first quarter ended 28 May, driven by 17.2% growth at Costa and a 14.3% improvement at Premier Inn.However, the restaurants unit, through which Whitbread operates under the Beefeater, Table Table, Brewers Fayre and Taybarns chains, increased sales by just 1.6%. Nevertheless, the company said it performed slightly ahead of a "soft" pub/restaurant market outside the M25.Group like-for-like sales were up 4.3% over the period, with Premier Inn and Costa growing 6.3% and 5%, respectively, while restaurant LFL sales rose just 0.1%.Whitbread reiterated guidance to open around 5,500 new Premier Inn UK rooms this financial year, along with 250 net Costa stores worldwide.The company also announced that it had brought forward the start date for new chief executive Alison Brittain to 7 December, from the 4 January 2016 initially.Brittain, currently the head of retail banking at Lloyds, will replace current frontman Andy Harrison who announced plans to retire in April.