Ghosts of Christmas Past

I don't want to seem eternally grumpy but.......I was just visited by The Agency Ghost of Christmas Past:
A Ranstad Care rep called me to see how things were going.
 I told her:
"The last time you guys called me, the first bloke said that I was just what they were looking for.
Ten minutes passed and the next woman said she wasn't sure whether I was just what they were looking for and ten minutes after that the same woman rang me back and told me that they wouldn't ever have anything for me in this lifetime.So I'm fine thankyou. How are you?"
She said something like "umm...er....well....sorry...."
And that was it.
They've gone again.
No doubt I'll hear from them in another twelve months and have to remind them what they said to me again....about the time someone new in the office needs to meet their targets...
Then I applied for a vacancy advertised on the internet, using my CV.
It didn't look like an agency was involved at all, but the Badenoch and Clark "Recruitment Consultancy"rang me about my application so I guess one must have been lurking in the woods somewhere.
I listened to the usual spiel and tried to remain awake.
Then I said: "Look, I have four recent CRB Enhanced Disclosure checks.
Totally clear.
No issues.
I really am NOT going to pay for another one simply so that I can sign up with you guys"
There was a short pause at the other end of the phone , then he said:
"No, no. As long as you have one from withing the last ten months that will be fine"
I was puzzled.
"Are you sure? All the other agencies told me I need to get another one done if I sign up with them, as "It's the Law""
He was sure. A recent one would be fine.
Well isn't that odd.
Do I smell something fishy?
Exactly what IS the legal position here.
I mean either the law is:
A) or it is:
B)
It really can't be both*
Having said that, he did say he'd be contacting me by email to get me signed up and I've heard absolutely nothing.
And that was a week ago....

*The government have not banned portability (the use of a disclosure obtained by another organisation) but they don’t advocate it and encourage businesses to make their own checks to ensure they are up to standard and nothing has been missed.
http://www.moneymagpie.com/article/767/de-mystifying-the-crb-check-your-questions-answered/

The above is all well and good when applied to full-time contracts, but when a person is enrolling with several different agencies at about the same time it appears to make no sense whatsoever.
Unless one has shares in one of the many private companies offering to carry out " CRB Personnel Checks".