Make the rent payment, that is the most important. Payday wont care if your tenancy is terminated as long as they get their money, it will probably make no difference at all your offering and what they take, they will want the agreed sum.
Lose your Debit Card and ring the bank now to tell them it has been lost and to make no further payments from it.
Make it clear in your letters that these are the 'maximum' payments you can make to them, include the first payment with the letter. No doubt you will get nasty letters, but keep up the payments you are offering and all will be well.