Real estate woes (advice)

[Charliewool]

With our vast array of occupations & professions on FFA, I thought someone here might be able to help with my dilemma.
I have had my home on the market since March. After 6 weeks of open days & inspections finally we had an offer that was appropriate, and we accepted their offer. Contract was signed, albeit "subject to finance", $25,000 deposit paid (5%), and settlement asked (by the buyer) was 30th June. Our agent put "SOLD" on the ads on net & in newspaper.
2 weeks before settlement their conveyancer contacted ours and asked for an extension due to finance paperwork not having been finalised. We agreed.
At 4pm on the last day of extension they asked for another extension due to further finance complications and we reluctantly agreed again.
This has happened TWICE more, with settlement pushed out til July 31st.
Meantime there have been 2 valuation inspections by banks on buyers behalf.
Today at close of business is the final day of the current extension to make the sale "unconditional" and I can see another extension being asked for!

What do I do? Do I grant it? or do I tell them to take a hike, which means starting from scratch and putting the property back on the market?

There is also the small matter of both myself & partner having both signed leases on rental properties, and myself having moved into mine. A mortgage, a lease, child payments and all the associated costs with managing THREE homes is NOT too appealing!
I have also been informed that the buyer gets his deposit back because of the Subject to finance clause.
Doesn't the vender have ANY rights at all?