Hi Newo. I wouldn't let the neighbour access through your garden if i was you, for the simple fact that if he says he needs a mini digger to excavate the foundation, then he will most probably be using a small dumper to remove the spoil too, because it will be quicker than a couple of barrows.
Also, if the builder damages your patio i doubt either your neighbour or builder will be willing to cough up 7000 euro to replace it.
Also, if the builder damages your patio i doubt either your neighbour or builder will be willing to cough up 7000 euro to replace it.