Cancelling building contract

Hi

First home owner based in WA

We signed up with our builder in December 2020 and paid 2k deposit. It has been 7 months now and just been told by the builder that they went someone to start with footings and encountered storm water drain in the way of putting the slab. They are blaming the land developer and not taking up any responsibility.

We settled our land in sept 2020 and if the slab is not down by September 2020, we will lose out on FHOG and have to repay stamp duty duty ( as the requirement is to get slab down within 1 year of settlement on land)

Adding to it, my partner who is on the contract and loan is now on maternity leaves and if the slab is not down by sept 2021, we will have to fork out 17k out of pocket ( loss of fhog and repay Stamp duty) .our lender will not increase the loan amount and loan will fall through due to change of circumstance affecting our borrowing .

Builder has been made aware of this and was given 5 days to respond but all they say is that they we will get back ASAP.


Any suggestions, we want it out and cancel contract due to delay and change in borrowing capacity

Thanks
Billy and bob