Not sure I follow your arithmetic.This years deficit will be £164 billion. We already owe nearly £900 billion. Our yearly interest is £40 billion.
We need cuts/tax rises of around £300 billion per year
If (as you say) this year's deficit will be £164b, we need a total of spending cuts + extra taxes of £164b to stop it getting worse.
If as you say our total debt is £900b, why do we need £300b per year? Are you expecting the total debt to be cleared in 3 years, or in 7? would you expect taxes to go down a lot after that?