HSBC has specialised ATMs which only take deposits of banknotes into HSBC (and FD and M&S) accounts. These are located inside branches and therefore are inaccessible when the branches are closed. However, HSBC tellers are only ever open 0900-1700 and so when the branch is open outside of these hours, the only option for depositing notes is the ATM.

Deposit ATMs are also available in Lloyds (and probably TSB) and Halifax. I'm not sure about Natwest and Barclays.

Withdrawal ATMs are located inside and outside branches, and those provided by banks can be used by any UK customer from any bank free of charge.

Santander has ATMs that can perform both withdrawals and deposits. These are located inside and outside branches. The ones inside branches are instantaneous (and one may be able to access these out of hours by swiping one's bank card to gain access into the branch when it is closed). The ones outside branches, AFAIK, just hold the notes until the staff come in the next banking day - though the ATM will warn you that your deposit will not be credited instantly.

BTW, I believe the actual British term is "cashpoint" - ATM is an Americanism.