Complex sentence: The group met once a week--initially on Tuesday evenings at 8:00 pm, later on Monday evenings--during term at No.4 Fitzwilliam Street, Philip and Hannah Hobsbaum's home near the university.
Split into simpler sentences: The group met once a week, initially on Tuesday evenings at 8:00pm, later on Monday evenings. During term time it met at No.4 Fitzwilliam Street, Philip and Hannah Hobsbaum's home near the university.