>how do these help? increasing landlord costs would result in them raising their rents to cover the difference
Actually, counter-intuitively, it would probably bring rents down.
A lot of housing is now held on to like a bar of gold and not used - previously expected to just keeping increasing in value. These taxes would arrest that rise and potentially cause a drop. This would lead to a lot of spare housing being rented out in an attempt to recoup investment losses.
Also, since it would push up costs for home owners it would make many of them bite the bullet and rent out a spare room to help with the mortgage repayments.
Since investment in new property in the UK (we're not talking about rural Iowa here), is determined primarily by plots of land becoming available it's unlikely to throttle new building.
> Eliminate mortgage interest tax deducations
how do these help? increasing landlord costs would result in them raising their rents to cover the difference
> Raise interest rates
this would result in lenders requiring higher deposits
(the others make sense)