I think the Royal mint has been particularly unfair with regard to the old £2 pieces. They minted over 30 million such coins (over 8 million for 1986, 7 million, 5 million etc for other years) in total and it is hardly surprising that some got into circulation. I remember paying £4 as a teenager for a 1986 coin housed in the usual packaging thinking that it will always have an intrinsic value of £2.
The Royal mint site currently states "The commemorative £2 coins were issued to mark special occasions rather than for use in general circulation. They are legal tender but contrary to popular belief this does not mean that banks and retailers automatically have to accept them. Indeed you will probably find that most banks and retailers refuse."
My feeling is that every piece of junk the Royal Mint make these days is marking some special (or not so special) occasion or event or cartoon character. The mintage of some of the old £2 coins are so much higher than the so called circulating Kew garden 50p for example. I would be surprised if they had told anyone in the 80s that such coins are not for circulating and so will not be accepted in banks. Since the £2 coin is a current denomination, I think The Royal Mint should do the decent thing and ask banks to let people exchange the old pieces if they wish to.
An episode of the Simpsons come to mind:
Woman: Would you like to buy some Itchy and Scratchy Money?
Homer: What's that?
Woman: Well it's money that's made just for the park... And it works just like regular money, but it's, er..."fun".
Bart: Do it, Dad.
Homer: Well, OK, if it's fun... let's see, uh...I'll take $1100 worth. (gets the money and he walks in and sees all the signs that show places prohibiting Itchy and Scratchy Money) Awwwww!