As a coin collector I have been searching for an undated new style 20p coin, both in my pocket change and also on Ebay.
Very noticable is the fact that a large number of ebayers are selling what they advertise as an "Undated 20p Coin" However, although the further details of the listing indicate that the date is present on the "Heads" side, the majority of the new coins have a date on the Queens head side, which is exactly what the Royal mint wanted to do. A "TRUE" undated coin is just that.....no date at all.
The listings can be misleading to anyone who is excited at the prospect of buying a piece of Royal Mint history, but please be aware of the exact details and read the listing VERY carefully.
Remember the basics...Undated means Undated....no date on either the Queens Head or the reverse side.
Another new misleading listing style is the advertising of "Updated" instead of "Undated". This has lead me a few times to a listing which is showing a picture of the Mule, but not selling the mule; only an Updated coin, i.e. the new 20p with date on the portrait. The seller has a small text in the listing with some caviat about the coin shown may not be the one you receive.
Good luck in you search and bidding. If you manage to buy a genuine undated coin, then a wise investment it will be.