OK, so it's a 100 year old house. It's going to have some damp, right? As far as I can tell from reading building survey report, the DPC needs re-doing as it was too low so has failed. From research that's looking like around 1k for a new one (terraced house).
This is the first building survey report I've seen. Have to say that they read pretty terrifying at first! 2.5k for this and 2k for that, £800 for the other etc..! But I took a deep breath and instead of panicking, whittled it down to the essentials. The DPC definitely needs doing. There's something about the dining room floor not being level, but I've lived in a wonky flat for years I think I'd fall over in a straight house 
and pointing was mentioned. The surveyors estimates for these works come to around 5k, but I'm assuming they're at the top of the bracket and the works don't cost as much (seen DPC priced at £900 not 2.5k for e.g.).
I'm thinking of asking for a 1k reduction in the offer price to reflect the essential DPC. Sound reasonable? I already offered nearly 3k below the asking price, which seller jumped at.
Seasoned house buyers opinions welcome! Am I being too nice?? Or am I being reasonable? Hard to know as a first timer.