I thought that they were a suspicious lot too soo I googled their mobile number and came accross this posting.
I found a Yorkie puppie on Gumtree and it turns out that their "Delivery Agency" does not exist, all of the company landlines are out of order, their website, www.pettransport7.com does not exist and they have a suspicious looking hotmail addresses, firstname.lastname@example.org, email@example.com and firstname.lastname@example.org...
Luckily alarm bells went off for me and I did not part with any cash... This is the second such scam I have come accross involving a "Delivery Agency" and "cash-up-front"
Please be ware.