I think your first step would be to contact the council and see exactly what alterations they allow tenants to make.Your council will no doubt have a website and will probably have an area where FAQ's regarding council housing is displayed
If you have enough money to contemplate such an undertaking why not take advice about buying the property.
Where would you be if after spending money to alter the house as you suggest the council changed its attitude to selling council houses and refused to sell to you.
Do some research and seek good advice before ploughing money into the house