Yes its true. We tried to get our kitchen modified, whilst house was at foundation level and it would have had to involve the local council + cost to us. In the end we decided against.
Our neighbours, though, had the "standard" build house modified (different bath and kitchen) and had to get the place inspected (and pay for themselves) by the local council before a completion certificate was issued. I think the building firms can issue a building certificate themselves if they are like the "show house" that the council has already approved. Builders we really helpful in accomodating their requirements as long as they paid. Don't tell them (previous owners) as the new owners who recently bougth the house have redone the kitchen as the layout was "crap".