Upon 'landing' at the POE we r duty bound to 'show' the Actual POF as required by the CIC [the No. of family members Funds Chart]. We maybe 'denied entry' for want of that. The IO has full right to 'return' us back w/out "completing" the 'record of landing'.
You asked, "How much in Cash"?
The answer is that we may not show anything 'in cash'. All that is required to have is a 'proof' of funds. Which can either be in Cash or Draft or Pre-arranged Bank Transfer etc. The combinations could be any, & multi formats are acceptable.
However, the 'ideal' situation is to carry 'some' cash, as the Draft would take sometime [usually 30 days] to materialize. Till then we'd need some funds for our daily routine, don't we?
About the Child Tax Benefit:
To my knowledge it is not linked to the POF at landing. It is linked to the No. of kids we have, the financial situation of the family, the job that we are doing -aka earnings, Bank statement, other obligations etc.
Your opinion that it'd be linked to the 'landing funds' is unfounded, as in any case we have to bring-in the minimum requirement as per CIC guideline. Yes, if we bring-in substantially more, it's another matter. 'Coz in that case our Bank a/c would reflect potential savings, which might reduce the CTB.
Hope that clarifies.
Qorax