From London:

Take the M2 Motorway (coast bound) until the A2 route to Canterbury. Continue directly into the city centre where you will automatically join the ring road. Pass through 4 separate roundabouts before finally turning right at 5th roundabout (A257 direction Littlebourne/Sandwich).

From Coast (Dover/Folkestone)

Take the A2 from the coast directly to Canterbury and take first exit for the City (also marked Sturry). Follow the road directly into the City Centre, but turn right (at lights) by Blockbuster Video (on right) onto A257 signposted Sandwich.