Under the Sexual Offences Act 1956, the maximum was two years, or, if tried by the magistrates' court, 6 months or £100 fine (!) or both (£100 was quite a lot of money in 1956). The judge was thinking of the old maximum for just one offence, as his starting point. He could have imposed consecutives or a mixture of concurrent and consecutives. It's bit of a legal nicety; the limit is because the 2003 Act is deemed to have created a new, redefined , offence when it redescribes an existing one. If the old Act had been in force but the penalties increased, he could have increased the sentence to the new level; that's what happened to the £100 fine (above). But he can still sentence in accordance with modern thinking, this being a case of multiple counts, he can do it by consecutives for the worst examples and concurrent for the rest, just as he could have done in the past.
Don't suppose that parents wanted to believe the child, but doing so, took the view that a) accusing Hall would get them nowhere b) he would not meet the girl again