This letter is very deceiving it looks like a bill for one or more of your domain names and is titled as an Expiry Notice. however it is a request to transfer your domain name which you will only notice if you read the underlying text.
If you do a google search for this company many of the results are from people being caught out by this.
If you do get a letter in the post from them just rip it up and put it in the bin as the cost is more than registering on there web site and in other places.
What makes it worse is that these letters are from an icann's accredited registrar(or at least they say they are) who are using WhoIs records to letter spam people.
p/s I could not find a category for domain name/internet related matters if there is a category for this. Mod's feel free to move this post