No bank holiday falls anywhere in the United Kingdom during September, and none does in October either. In England, Wales and Northern Ireland the run from the August holiday to Christmas is the longest gap of the year; Scotland breaks it with St Andrew's Day at the end of November, but nowhere else does.
September closes the third calendar quarter of 2030 on the 30th, and 30 September is also the financial year end for a substantial number of British companies. The tax year, by contrast, is not quite six months old — the two systems are as far out of alignment here as they ever get.
September 2030 closes with the autumn term settled and the evenings drawing in hard. October follows with the clocks going back, half term in the last week or two, the paper tax return deadline and Halloween all inside the same month.