Yes, then ought to be than.
I was quite surprised the first time I came across this misspelling, which was a few years ago. But the explosion of material published on the internet without the attention of a copy editor (and sometimes even with such attention, as presumably here, the Echo being a reputable newspaper) has made me realize how very widespread it is. (Since there is also a perfectly good word then, it would not be trapped by a simple spellchecker.)
There are plenty of other examples to be found on the web.
And yet I don’t think people commonly misspell ran as (w)ren, or tan as ten. In all core native accents of English the words of the TRAP set are consistently distinguished from those of the DRESS set.
So what’s going on?
In speech, the word than is almost always pronounced in its weak form, ðən.
ˈbetə ðən ˈevə
ˈmɔː ðən ju kʊd biˈliːv
ˈmɔː ðən ˈʌðə dʒæbz
It is difficult to envisage a context in which one would want to accent it, thereby triggering the strong form. (I exclude the obvious one of naming the word rather than using it, as in ”How do you spell ‘than’?”.)
The only way to trigger an obligatory strong form in ordinary conversation seems to be by resorting to stranding (blog, 28 May 2008).
The syntax here involves the fronting of a mouse, with the consequence that than is stranded, deprived of the NP it governs. As with prepositions and indeed all other function words, such stranding in English calls for the use of the strong form of the stranded item. The word normally remains unaccented.
I would say
I wonder if anyone actually pronounces the strong form as ðen (to rhyme with ten). That is not inconceivable, given the extreme rarity of strong than and therefore the extreme rarity of opportunities for the language-acquiring child to hear how it is pronounced. (After all, the usual ðən might result from the weakening of any of putative ðen, ðæn, ðʌn, ðɑːn, ðɒn — compare the strong and weak forms of them, at, us, are, from.)
You’d think, though, that most children would have been exposed somewhere along the line to such utterances as Who are you bigger than? Who is Mary younger than? Which of your brothers are you older than?
Nine is one fewer ðən ten. Ten is what nine is one fewer ðæn.