Trains run from both King's Cross and Liverpool Street stations in London to Cambridge station. There are also services from Peterborough and Stansted Airport (among many others). You can get information about train timetables over the whole country from National Rail (and other sources). Cambridge station is about 5 km from the Cavendish - it is probably best to take a taxi. The location of the taxi rank is signposted outside the station entrance. It is also possible to use the U bus (which runs on a 15-minute schedule), which runs from Addenbrooke's Hospital via the railway station to just outside the Cavendish Laboratory and then on to the Madingley Road Park and Ride