Hello Grandee,suggest you consider SUNDEALA board 9mm 8x4 ft £86 delivered if you are going into this hobby big time.
Its advantage is that your track pins go into the board easily and it is a great time saver ( with all those bent pins having to be reinserted a non entity) This board sits on top of your base board, you dont say what the dims for this are. Select track pins carefully and determine just how is best for you to pin the sleepers to the board.
Watch the weight of all this and its. manoeuvrability
If £86 is a worrying facctor, ask on here just who else would recommend it for 1st choice.
Best of luck.