Rule for refund of booking amt of flat

Location/place: Pune

Hi All,

I have booked one flat in Pune area by paying by cheque of Rs. 50000.
After submit file for loan but it was not cleared and in the mean time i pay remaining R.s 200000 through cheque to builder.

But due to some personal problem i want to cancel flat. so i want to get refund.(i.e Rs 250000) but builder has charging 20% on total amount(which was communicated verbally and not written this on broshar doc).

Also when i checked the town planning docs that flat is not legeal.

Please advise me in this case.
How can i get my refund amount as my financial health is not that much to give 20% amt to builder.

thanks in advance for your valuable suggestions.

Thanks,
Sachin

Please