Agree with all the posts ^^.
Surveyors are going to point out every last thing that needs doing, to cover their backs. If something else significant emerges after you buy the place, you could sue them.
Estate agents get aggressive when they can see their commission, and possibly also a precarious chain, disappearing in front of their eyes. They will also come over heavy-handed with a first-time buyer if they think that they can get away with it.
How much is the £3.5k compared to the asking price (which I assume you offered?)
Regulations for anything and everything move faster than the speed of light, especially for electrical stuff.
Ask the builder for the real implications of the cross-bracing issue. There are millions of properties out there that won't comply with "current regulations" because they were built decades before the regulations were revised. Funnily enough, they are all still standing ... (I think ours is probably one of them.)
Are the window frames uPVC double glazed or something else - wood, aluminium? What does the surveyor say about them?
If they are uPVC, and the glass is simply "blown" (cloudy), the cost to replace it is really low unless it is fancy leaded stuff.