This is quite an old thread now but with the interest in 50ps in recent years I believe it should be revived!
In response to an earlier post:
Royal Mint is normally rather mute on how or when coins are released. Part of it is due to demand...
I do want to point out that
The Royal Mint can sometimes be quite out of date. On their website they provided mintage figures for the 2012-2016 Rio £2...these appeared to be quite low, however, they then released a LARGE quantity of the same coin in 2013 still dated 2012.
ebay has seen these coins reach large amounts on false pretenses...just a warning to you all