ATTENTION! We have tried to contact you, It is important we speak to you today. Please call 08445715179 quoting your reference 121190. Thank You.
In this case the sender's number was +447453215347 (owned by Virgin Media Wholesale Ltd, but operated by a third party). The catch is that the calls to an 0844 number can cost up to 40p per minute (see more details here), a large chunk of which goes into the operator's pockets. So what happens when you ring back? You get put on hold.. and left on hold until you have racked up a significant bill.
Sadly, I don't know who is behind this scam, and in this case it was illegally sent to a TPS-registered number.
If you get one of these, you should forward the spam and the sender's number to your carrier. In the came of T-Mobile, O2 and Orange the number to report to is 7726 ("SPAM"). Vodafone customers should use 87726 ("VSPAM") and Three customers should use 37726 ("3SPAM"). Hopefully the carriers will act if there are enough complaints. You should also send a complaint to the ICO who may be able to take more serious action against these spammers.