http://www.ukphoneinfo.com/search.php?GNG=447024056048&Submit=Submit&d=nl
"Numbers must start with `0' if they are area codes or full UK telephone numbers, or start with `1' if they are access/short codes.
Numbers starting with digits 2-9 are for local, within exchange area, calls."
More:
(447) 02405 604 8
"024 National Dialling expansion
Section: Codes in Range 1000-2999 - Geographic Numbers
Warning:
Numbers starting 02405 60 are probably not valid.
Oftel records show that numbers starting 02405 60 are free, and available for allocation."