UK Landlord Forum / Life

I recently moved out of my privately rented property on 12/11/18.
My landlady told me and my family on 5/10/18 that she would be selling the house so we had to find somewhere else to live. She eventually served us a proper Section 21 notice on 20/10/18 after we had gone to the local council and told them we were threatened with becoming homeless. They informed her that the handwritten letter that she had provided wouldn't suffice and she would need to do the Section 21.
We moved in to the property 30/10/17. She let us pay the deposit of £600 in monthly instalments on top of our £600 monthly rent. So we paid £700 for 6 months. However, upon moving into the property she would not let us pay the rent via bank transfer/direct debit all because she didn't want any trace of it. She made us pay it in cash, in person every month all to avoid tax on it.
I should also mention she abruptly informed us about selling the house after a visit from our energy supplier to instal smart meters. They found the gas fireplace to be unsafe and needed it disconnected in order to carry on with the installation. She was not happy and within the hour, popped round in person and said all the phone calls were too stressful and so her and her husband have decided to sell the house. We have only called her with one problem prior to that which was a leak in the living room ceiling from the en suite - which she never fixed.
She admitted to the guy who came to install the smart meters that she had never done any gas safety checks on the property after he questioned her about it.
I know we paid the deposit in instalments but after the last payment I know she didn't put it in a DPS.
We always paid our rent, the property is clean. She requested for the garden to be tidied before we leave otherwise she would take it from our deposit so two days after we moved out my partner and his friend (who has a gardening business) went round to the property to tidy it all up.
When we informed her we had our moving date she questioned the rent. We hadn't paid it yet but my partner told her she could just give us £300 back out the deposit once we moved because we were leaving halfway through the month. She agreed to this and that's when she mentioned the garden.
She's always been a difficult lady to communicate with. It's definitely stressed us out having to move so suddenly. I'm 7 months pregnant and have a 4 year old son and she gave us 2 months to move out. My partner text her the same afternoon he'd done the garden (14/11/18) and informed her it was all done and we would like the deposit back asap as moving so suddenly has left us short. She has not responded at all.
I'm just wondering what kind of position we are in and if we can speed up the process along? Surely she is no position to withhold the deposit from us?
Thanks Lauren

The only real option you have is to sue her for the deposit back, plus deposit penalties if I were you. The problem you'll have is proving that you paid a deposit. If you think you can evidence it sufficiently to convince a judge, then letter before action and then court.