I grew up in Guildford, and enjoyed it hugely.
My family lived in the 'cheap seats' in Bellfields estate, on the edge of the common. The town itself is nice, cobbled street, reasonable collection of shops, the theatre is just about hanging on etc. (The christmas panto with Peter Gordon is always particularly good).
If i had your budget, i'd probably avoid buying in Bellfields, and would certainly avoid buying the Park Barn estate.
The Onslow Village was always perfectly nice, so long as you were far enough away from the hogs back. Elsewise toward pewley hill was very posh, and i think a previous poster quite rightly recomended some of the surrounding villages (Shamley Green, Shere is beautiful) etc.
Secondary Schools wise, (and remember i am easily 15 years out of date) my impressions were roughly thus:
Christ College, on it's way up, but a way to go. (Rebuilt after being burnt down, new facilities etc).
County School, on it's way down, but not too bad. (Specialist music college, back in the day).
George Abbot, a good school but massive.
Royal Gramma/Guildford High, incredible academically, but violently expensive and impossible to get into.
Good luck with the search!