Red letter day?

On the front and inside cover of the 'Simply the Best' mini-catalogue it says 'simply spend over £100 and win a red letter day'.

I know this puts red letters on my bank account but on the 2 orders I've placed over £100 since this came out nothing else has happenned.

Do they get held up to the end of the month, then to overwhelm me with red letters? What should I expect? Are they nice letters or red angry ones? Do they turn the sun red on that day or do Cooksons deliver my order in a red van and roll out a red carpet to my workshop door?

Can anyone enlighten me?

LOL
Red letter days are usually 'experience' events - hot air ballooning, race car driving, that kind of thing :)