I recommend using BillPay with a debit card at https://www.santanderbillpayment.co.uk/hmrc/scripts/help3.asp.
It’s instant, although the confirmation email can take 2-3 days.
If not using BillPay, it’s now too late for BACS if your bank takes three working days for transfers. If your bank does FPS same-day payments, that’s OK, otherwise you’ll need to ask for a same-day CHAPS payment to be set up.
https://www.gov.uk/pay-self-assessment-tax-bill/bank-details shows the relevant accounts. HMRC suggest using Cumbernauld details if in doubt as to whether to pay to Cumbernauld or Shipley – in practice it seems that either is fine. For any electronic payment you will need your 10-digit tax reference.