Functional bikes. Not Porn not Anti

I'm thinking of building up a one on pomp with disc brakes and hub gears - no idea of budget as of yet. I'm trying to save some cash so it'll be a slow process. What should I budget for something like this? (Absolutely no idea when it comes to disc brakes or hub gears)

1. You live in Norfolk.
   
2. Got a perfectly good all-round bike.
   
3. Singlespeed.