I have cradle 000051785A which is suitable for TomTom One V4 and V5, AKA IQ routes. There is (or was) another cradle suitable for TomTom One V3.
The trouble is that AFAIK all these TomToms are obsolete. I bought a refurbished One V5 direct from TomTom earlier this year and it works fine in the 000051785A cradle.
I believe I read that there is now an adaptor to suit the current TomTom Start but I can't find the reference - if I can find it I'll post more info.
Some people have modified the 000051785A to suit the more recent models with wider screen, see:-
http://www.seatcupra.net/forums/showthread.php?t=304102