イギリスでは土曜日はもとより金曜の午後まで休みにしている会社もある。 Translation is:
- In the UK, some companies are closed on Saturdays as well as Friday afternoons.
In the English version, 'as well as' acts on 'Friday afternoon' i.e 'as well as starting from friday after noon,the companies close'.
- In the Japanese version: the word-by-word translation of the sentence looks to me like: In England, not just Saturday, but there there are also companies where until Friday afternoon a rest is made.
From what i understood from the sentence, the も must relate between 'Saturday' and 'Until Friday afternoon' NOT '土曜日' and '金曜の午後まで休みにしている会社'.