LONDON,(Reuters) - British manufacturing grew strongly in September and orders flowed in at an above-average rate, adding to signs the economy has avoided an immediate hit from June's Brexit vote, an industry survey showed on Thursday.

The Confederation for British Industry's total order book balance held at -5, well above its long-run average of -15 and as expected in a Reuters poll of economists.

Output expectations for the next three months touched a three-month high, although export order growth eased slightly from August's two-year high.

"It's good to see that manufacturers are enjoying a lingering summer with output running at a strong pace and manufacturers' order books remaining solid, particularly amongst the food, drink and motor vehicles sectors," CBI chief economist Rain Newton-Smith said.

"Our members tell us and our surveys show that the fall in sterling has boosted international competitiveness for many businesses, with export order books remaining well above average in September, despite weakening slightly," she added.

But Newton-Smith said there would be plenty of challenges ahead for manufacturers as the process of leaving the EU unfurls, meaning finance minister Philip Hammond should focus on investment when he outlines budget plans on Nov. 23.

The CBI survey of 481 manufacturers was conducted between Aug. 24 and Sept. 14.

(Reporting by Andy Bruce, editing by David Milliken)