Went and checked another M25 and hate to say it, but you are right. The fuel inlet was 11/16" and the base was 27mm, which I don't normally carry so must've brought from home for the occasion.Just to clarify if we're talking about removing the injector body from the head the 22mm came nowhere close to fitting. The 27mm fit like a glove.
The 7/8" was the size of the top of the injector. I took them apart to inspect and clean internally so did use that size then decided to just replace them.