If one does an auto coupled ILS approach in say CAT 3a conditions then the ILS Localiser Sensitive Area (LSA) will be safeguarded, and hence the risk of disruption to the signal reduced.
If you do the same approach to a CAT 1 ILS the LSA will not be safeguarded, nor will ATC increase approach separation.
You may not be concerned about this, but I thought I'd mention it.
Sir George Cayley