The ISOFIX guides came with my Base M.
They were excellent to help guide the rails for isofix from the base, as my isofix points were buried deep in the backseat.
With this on, attaching a base is so easy you could do it eyes closed. I’ve basically done it in the middle of the night.
I ordered some ISOFIX Guides on the 23rd, and they are still not here in Christchurch on the 6th. The shipping company seems to be taking their time. I should have ordered from China, it might have been quicker.