You bank will usually allow a 100% mortgage on the build cost (seeing as it will surely be worth more after its built), and the council levy is seem as part of the necessary build cost. And its not really that much extra. Its not unusual that a 2000 sq.ft house that cost 200k to build would be worth 400k(ish) when built. Thats a loan-to-value of 50%, which is VERY attractive to the bank.
In fact, even if your build cost is 200k, you can still borrow any amount abouve that (furniture, car, whatever), within affordability and reason.