By Andy Silvester The English wine industry is toasting the start of what it hopes will be a bumper summer for homegrown vintages. The once-maligned sector, based mainly in the south-east, has shown extraordinary growth in recent years and yesterday insiders told City A.M. it was set for the best summer of sales yet. Those hopes were boosted overnight by the award of a host of high-profile awards for English wines at the prestigious Decanter World Wine Awards. The UK posted a record-breaking year for total medals awarded including a first-ever ‘Best in Show’ for English sparkling rose to Chape…