Definitely need building regs may need planning for "change of use" and they will assess the parking situation even though you probably don't park your car in the garage.
You need to consider access, we put a door through from the hall.
Depending on the house, you may be able to retain storage at the front and keep the garage door or replace the garage door with a window. If you do the latter don't just infill the gap with a massive window. To blend it in match it in size with your existing windows. That is what we did.
Don't underestimate how much junk you will have to store somewhere else if you convert the whole garage. I did the front of mine and retained a 6ft deep space at the back to store everything. Or alternatively think about filling an entire wall with storage cupboards. We have a shed for lawn mower etc.
Over-do insulation, don't just do it to building regs standard go above that. I did a double garage 5 years ago, 2 radiators, two new windows and a hell of a lot of flooring. Had a wall built across the entire double garage for the storage bit and a fire door to access the storage bit from the house. Moved alarm cables, sockets, moved a soil pipe, relocated a loft hatch, etc Everything in was about £11k but it did include a few extra bits.
If your garage is completely integral then it will be double skinned (inside and outside wall of bricks meaning it has a cavity wall) if it is to the side or semi integral then you will have to seriously insulate the exterior wall.