Let's see:
- Spam sent to email addresses that only exist to trap spam? CHECK
- Spam comes from dynamic consumer ISP space? CHECK
- Envelope sender forged? CHECK
- Date: header a couple of hours in the future? CHECK
- "Content-Transfer-Encoding: 7bit" but includes 8-bit characters? CHECK
- Text mentions "double opt-in" CHECK
- Spamvertized website operates out of Latvia, not the UK? CHECK
It could alternatively be a come-on for a Russian Brides style scam.