Thanks that is a very tempting offer, but in this case, buy your own!!
http://shop.ebay.co.uk/i.html?_nkw=25+Pence+Crown&_sacat=0&_odkw=Queen+Mother+80th+birthday+coin+%2825+Pence+Crown%29+1980&_osacat=0&_trksid=p3286.c0.m270.l1313Some more info on the coin, thanks to the interweb...
By 1990 inflation had meant that to issue a large coin at 25p would result in a large portion of the income being taken up in minting the coin, and the purchasing power of the first commemorative crown of 1935 was well over ten times that of 25p in 1990. As a result it was decided that future issues of crown sized coins would have a face value of five pounds.
It is a misnomer to call them crowns, however, as the crown has been five shillings since 1551. They are correctly referred to as crown-sized coins.
Weight: 28.28 grams, Diameter 38.61 mm, cupronickel, although silver and gold proofs are known.
Starting in 2009 the Royal Mint started to issue large numbers of Non-circulating Legal Tender (NCLT) crowns issued only in bullion for the London Olympics. Until I get further information from the Royal Mint I will not be listing these items.
While technically five pound coins are legal tender, banks are reluctant to accept them. Consequently traders are also likely to refuse them.
So far there have been twenty four crown-sized five pound coins.
1990 Queen Mother's 90th Birthday
Obverse: Second Portrait, ELIZABETH II DEI GRATIA REGINA F D above FIVE POUNDS below
Reverse: Crown over two intertwined E's, rose & thistle QUEEN ELIZABETH THE QUEEN MOTHER 1900 1990
Edge: Milled
for those really into you coin collecting (which doesn't include looking down the sofa to help buy your new bat..)
http://www.royalmint.com/Corporate/facts/coins/FivePoundCoin.aspx