Any pointers to ridding me of the problem of "withheld calling" - Ideally the handset would silently answer and play a recording telling people that there call cant proceed because there number is withheld, otherwise simply rejecting to the network busy signal will be fine.
It's not something I've ever heard of anybody wanting to do. Most phones these days support some form of caller profiles so you could set up a list of "accepted" numbers that will cause your phone to ring and for anybody else it will automatically go to voicemail. The only phone I've ever come across that could play a phyical message to a caller was an old analogue Motorola that has it's own built in answerphone/voicemail.
I take it a manual rejection using the 'end' key is not what you are after?
Some phones (eg cdma sanyo - sorry i dont know much about gsm phones), allow you to set a ringtone for no caller id. I used to set mine to silent, then blocked id calls would ring through, but not make a noise, and eventually hit the voicemail system.
I dont think you can send some calls to voicemail and some to busy signal though...
Samsungs often have a built in answerphone, (Telecom n361, n391 do) you could setup a voice greeting to play "you are calling from withheld number, please state whom you are.... BEEP" and you can "grab" the call when they start speaking (press talk)
I seem to remember my Sanyo 4920 allowed up to 15 seconds or so of "call screening" along playing a different ringtones (mine played something shocking so I knew to avoid it)
GSM phones, Try Samsungs and maybe Motorola The only other phones which I know had built in Answermachines were the Motorola Elite (025 flip) Startac 9000 (025 Clamshell)