There are so many scams around which work on the basis of scare tactics, for example: "...someone is trying to register yourdomain.co.uk and we thought you might like to take advantage and register it (through us) before the other individual does and you could lose it for good."
I treat all these with a pinch of salt.
In the real world, if the domain name is registered in good time and renewed in advance, it should be no problem. I have sent several e-mails to mu clients to watch out for and to avoid these and similar scams.
Useful reminder about domain name renewals. [nominet.net]
engine - never treat them with a pinch of salt - scammers / fraudsters are criminals and should be reported to the police and the domain registration authorities.
you might also like to report it to domainscams.com - there is an interesting one there about Domain Registry of Canada and the legal action taken against them - they are currently sending out false invoices as Domain Registry of Europe and have been reported to the police and other authorities in the UK and USA