Okay being C of E if you can get a Vicar/Pastor letter will mean you can guarantee a place at Queen Eleanor's or Holy Trinity depending on where you live, but you can probably get into those or other good primaries anyway.
Secondary is more of an issue. Guildford has 5 State secondaries, 3 of which are next to large council estates, which does affect intake; they are King's, Christ's College and George Abbot. One, St Peter's is Catholic, and at present (didn't used to be the case and school transport changes could change it) you have little chance of getting in unless you are a Catholic, well getting in in year 7. Then there is Guildford County, the old girls grammar, used to be the most sought after, and still gives pretty good results, 66% get 5 good GCSEs.
None of the schools are dreadful, none for instance would put metal detectors on the entrances.
However if you are living close to London Road Station or the main station you are probably just looking at George Abbot and County (unless things change with St Peter's). I know people who have chosen County over George Abbot, people who have had problems at both. I would suggest if it is important to you, that you contact the schools (asap or after the end of October) to visit. People do visit schools all the time here, September and October are likely to be busy though.
However schools do also change a lot, I have heard rumours of change in the reputations in Godalming schools for instance.
Another option is to live in the villages that are part of the Howard of Effingham catchment, which is a lovely school.