My understanding was that the Earth that Arthur found and on which he met Fenchurch in So Long and Thanks for all the Fish was an Earth that was found in another dimension which the dolphins then used to replace the destroyed Earth.
And then the fling of hope, the finding of a shadow Earth in the implications of enfolded time, submerged dimensions, the pull of parallels, the deep pull, the spin of will, the hurl and split of it, the fight. A new Earth pulled into replacement, the dolphins gone.
This is in contrast with Mostly Harmless, where it is quite clear that Arthur was traveling through dimensions and ended up on an Earth in another dimension.
Yet this seems to be contradicted in the introduction of And Another Thing (which, by the mention of Fenchurch, is clearly referring to So Long and Thanks for all the Fish):
Arthur Dent eventually returned to the hole in space where the Earth used to be and discovered that the hole had been filled by an Earth-sized planet that looked and behaved remarkably like Earth. In fact this planet was an Earth, just not Arthur’s. Not this Arthur’s, at any rate. Because his home planet was at the centre of a Plural zone, the Arthur we are concerned with had found himself shuffled along the dimensional axis to an Earth that had never been destroyed by Vogons. This rather made our Arthur’s day, and his usually pessimistic mood was further improved when he encountered Fenchurch, his soulmate. Luckily this idyllic period was not cut short by bumping into any alternate Universe Arthurs who may have been wandering around, possibly in Los Angeles working for the BBC.
So did Eoin Colfer mess up? Or am I missing something?