Royal Holloway, University of London is located in Egham, Surrey, a forty minute journey from London Waterloo station or a fifteen minute drive on the M25 from Heathrow airport. A taxi from Egham train station costs around £ 5. If you are coming from Heathrow, the University suggests reserving a local taxi ahead of time as they say the London black cabs can be expensive.
See detailed travel instructions here.
See the schedule for trains from London Waterloo to Egham here.