Colchester is by train 50 minutes away from London. Most convenient/closest airports are London-Stansted (about 60 minutes by bus to Colchester; 110 minutes using a direct bus connection to the University of Essex; taxi about 60 minutes to the University), London-Southend (about 90 minutes by train) and London-City-Airport (about 90 minutes by DLR, London Underground and train). London-Gatwick, London-Luton and London-Heathrow may take 2 to 3 hours by train and London Underground.
A taxi from Colchester station to the University takes 10 to 20 minutes. The following bus services run through the campus connecting it to and from Colchester town centre, Colchester Station, and Wivenhoe: 61, 62, 74/74A, 75, 76 and 87.
Further information about travelling to University of Essex can be found on the university webpage.