[Property] Buying a new build. Am I getting a good deal?

Hello!

So I'm looking at reserving a flat 40 miles outside of London. It's a new build 1 bed top floor as part of a 3 floor block. Builder is Taylor Wimpey. I think 6 flats in all. I'll be commuting into London but pay under 100 train costs every month due to my job. Train takes between 30 minutes and an hour into London.

So I'm putting down 20k on a 185k flat. The builder is paying my stamp duty (1,200) and 1k of legal fees if I use their solicitor and broker (I am aware that I shouldn't be using theirs but it's something I still need to look into). I'll probably be looking at paying 600-650 pcm repayments on the mortgage. I wont be using the help to buy to avoid having to pay anything back after 5 years.

I'm making 37k.

It's a 125 year lease and ground rent is 200 p/a and goes up by RPI every 10 years. Service charge is £1283.

Ive tried negotiating but all I've managed to get is the stamp duty. Not even carpets. Would you say that's an attractive deal? I haven't been given the lease details but before I hand over the holding deposit I'll be talking to them about a refund if I don't like the terms.

Just making sure I'm not falling into a trap.

Cheers!