Garage conversions do not generally require planning permission providing works are integral, i.e. you are not creating a free-standing newly habitable building.
You will have to adhere to building regulations for insulation, utilities, windows etc.
A quick call to your Local planning office will confirm if there are any exceptions in your area. Otherwise this is usually a straight forward job which any good builder will do for you.
Hope this helps

If you want to use your garage as extra rooms then you will need to put in an application for change of use.

I think you will require permitted planning

Hi you will need building regs . You will have to upgrade the insulation on walls,floor and ceiling. You will need architect drawings as to the building regs but the lawful change of habitat will also be needed.you could do this under building notice . But I wouldn’t do this as building control can change anything at any time