As has been mentioned, avoid HTB and get as big a deposit as you can. I'm also always amazed with the house prices up north.
Regarding new builds - TW are a 4 star builder, so should be pretty good. Not like Persimmon or any of those shocking ones.
As for what you can get, it does vary massively - if there is a stock plot that they can't shift, there will be flooring, grass, appliances, stamp duty, legal fees, £5k John Lewis vouchers, moving costs and all sorts thrown in. As you're buying off plan, with a long wait, I suspect you'll be lucky to get much of that at all - can't hurt to ask for something extra though.