Two rules related to this always come up:
1) "If an abbreviation is used for the unit of measure, the quantity should always be expressed by a numeral" (Chicago 14th Ed., 8.15). [No problems here in the case at hand, but thought I'd mention it.]
2) "A word space is used between the numerical and the abbreviation." (Chicago 14th Ed., 14.49)
In short, you are correct. It should be "their 26 m dish" and not "26m dish."
However, as always, certain considerations may be given.
This guideline "Abbreviations used with numerals should not be separated from the numerals" (6.55) is often misinterpreted as meaning that there should be no space, but it is really talking only about line breaks. A line break should never separate a numeral from its abbreviated unit designation.
If there is ground in a plain-text environment for permitting the elimination of the space between the amount and the unit designation, it is in saying that without the benefit of a non-breaking space, we value the no-line-break rule above the spacing rule. (I'm not saying that is necessarily the choice I'd make, only that this is the logical ground upon which you would justify it.)
There is also the interesting question -- which does apply to the case at hand -- in which the quantity and the unit designation are being used as a compound adjective. Typically, you hyphenate compound adjectives. There is a decent argument to be made that it should be "their 26-m dish" or "the 100-Mbps port," but the fact is that nobody "goes there" on this issue. This is probably due to the fact that the hyphen when used with numbers primarily means "minus" or "negative" combined with the fact that the compound adjective issue itself is a difficult concept to grasp.
In virtually all cases, I enforce the spacing rule (with the common and still ambiguous exception of the degree mark for temperature -- there's always an exception it seems).
Computer people seem to be the worst at being consistent with this. I can also be talked into making exceptions for marketing and branding situations in which "the 16 MB version," for example, is a compound adjective. I can begrudgingly go along with "the 16MB version," but that doesn't mean I don't think it is wrong. =)