By the way isn't 44 the international number for the UK. i.e. when calling a number in the UK from overseas?
Yes, but calling +44<phone number> doesn't cost any more if you're in the UK. I add all numbers into my mobile with +44 so that they work when I use the phone abroad.
On the original subject, spammers are getting a bit cleverer. My mobile number is out in the world as I accidentally forgot to remove my work email signature (with it in) from an email to a public mailing list (albeit a work related one). If you know what to google for you can find it pretty easily. It was a nightmare for a couple of months as lots of our customers were calling me directly and also IM-ing me.
The idea behind it is that the more information they provide you the less likely you are to think it is spam.
It's like the "bank calling" scam where, to prove they are the bank, they tell you your name, address, phonenumber, date of birth, card number and card expiry date. They then ask you for the CVV digits on the back of the card to prove who you are. Some people are fooled into giving them because they think it must be the bank if they know all of those details. Instead, they've just done their research and the CVV digits were the last piece of the puzzle they need to go crazy with your card.
Anyway. Don't worry about it, there's nothing you can do about the email anyway. You know it's spam so just delete it.