By Sachin Ravikumar LONDON (Reuters) -Thousands of BT call centre and engineering staff voted on Thursday to strike over demands for better pay at the telecoms group, the latest in wave of labour disputes across industries that threatens a summer of disruption in Britain. Almost 96% of roughly 21,000 BT Openreach engineers voted in favour of a strike, the Communication Workers Union (CWU) said in a press briefing. Some 91.5% of BT Group workers who voted, many of them call centre staff, also favoured a strike, the union said. Any strike — which would be the first in 35 years at the telecoms gr…