Many thanks for these replies. Sanseri, following your prod I compleained to the vendor, showing him precisely why the pen was bad. After a fair bit of bluster he accepted what I said - and refunded my cash! He's now going to contact the people he got it from, so forth. So: all's well that ends well.
Slimfish - if you have more photos and/or tips about detecting fake sonnets, I for one would be very grateful.
There is a good vid on You tube from Waski, link below.
These pens have been around for some years now and they seem to come along in waves, all is quiet for a couple of months and then the market becomes flooded again. I must say that the quality of the fakes is not too bad, they can fool a lot of people who are attracted by the low price of under £10.
There is one prolific seller, from Devon if I recall correctly, I had better not give his full name but it begins with 'aged', although I think he has more than one account, perhaps avoid all Devon sellers of low priced Parkers. Oddly he holds his hands up very quickly if you point out that he has sold a fake. Ebay have been told but appear to have taken little or no action.
A couple of tips, the quality of the engraving is not as good as Parker, for example on the clip. The finish is often a little too brassy and shiny. the seller makes some odd claims such as 'takes Parker or International cartridges', the engraving on the nib is much worse than Parker. The pen is not sold with a Parker box or paperwork.
Waski You Tube clip