FROM CAVERNS INTO TOWN: Heathrow Express' central station will herald a new era of spacious subterranean public transport in the UK when it opens to passengers in June. Passion and enthusiasm for the project expressed last Thursday by its chairman Rod Hoare as the completed station was formally handed over by fit out contractor Laing-Bailey, were more than justified by the pristine caverns he was showing off. Trial trains are already running in and out of the station independently of the current 'Fast Train' public service - which uses a fleet of buses to transfer passengers to the airport from a temporary station outside. But Hoare admitted that the opening date of the tunnelled section linking beneath Heathrow to the central terminals and terminal 4 had now slipped a few days to 'early to mid-June'. The new central terminal area station concourse leads via a series of wide passages to the platform tunnels on either side. Passenger flow is interrupted only by a tubular steel comb to stop baggage trolleys rolling off the platform. Journey time to Paddington will be 15 minutes. Managing director Ben Harding said that the proposed 30 minute service to St Pancras could be available by the end of 2000. Talks are under way with Railtrack on electrification of the Dudden Hill branch which would make the connection.