One of the reason's that property in and around Guildford is so expensive is due to the fact that it is on the main railway line to London. If you make sure you catch the direct line (only usually stopping at Woking) you will be in the capital in 30 mins!
Guildford taxi ranks are everywhere in the city. Outside the train station, next to the Friary Shopping Centre and at the bottom of North Street on the other side of the road from the Electric Theatre. Taxis can also be booked by phone and here are the details of the company I used everyday while I was in Guildford and travelling to and from London on business.