By Laura McGuire Hard-pressed punters could be set for another blow in October as a new law looks set to push up the price of a pint across London. Sticky inflation and supply pressures facing pub owners have seen the cost of a beer or larger surge over the past year, with the average boozer now charging £6.75. But this could rise to a steep £7.15 across London later in the year. The average price of a pint could jump after legislation impacting hospitality staff tips is enacted this autumn, according to a new study by hospitality technology brandThree Rocks®, Under the new rules, known as the…