Thank you all for your responses. As the pen is so new I contacted
Parker (er Waterman) and received the following responses: -

**********
Dear Andy

I was concerned to hear of the problems you are experiencing with your
writing instrument.

So that I can help would you please send the item to the address at the
top of this letter and I will look into the matter personally. Could
you please enclose a covering letter and your full name and address.

If you wish to have the repair considered under the terms of our
guarantee you will need to enclose your stamped warranty booklet or
proof of purchase such as a receipt.

I suggest that you package the item securely to avoid damage in the
post and if you send it by recorded delivery you will be able to keep a
track.

I hope this information is of help.

**********

We do not recommend the use of other makes of ink in either the Parker
or Waterman brands, they are not compatible.

You can however, use either Waterman or Parker ink in either of our
models but only if you are using bottled ink, the cartridges, will not
fit. The only colour that is not compatible is the Waterman black, you
can only use this in the Waterman fountain pen.

Our technicians suggestthat you only flush a nib unit out with cold
water. However, you could try soaking the nib unit in cold water
overnight (this is the nib and the shell(the bit your grip)and then tap
the unit against a lint free cloth and put a fresh supply of either
Parker or Waterman ink. Our ink has a shelf life of two years, after
this we recommend that you obtain a fresh supply.
***********

The irony was that I was looking at a Waterman Edson last night, as I
have for several nights, and my partner offered to buy one for me.
This would be a not inconsiderable purchase for her, but if the pen is
unable to use inks such as Noodlers then it is a non-starter.

I have decided to follow the Parker route and wash out the pen and
refill it with Quink as much as it pains me to do so. If there is
still a problem the pen can be returned, but being an xmas present the
receipt is now long since disposed of and needless to say the shop have
not stamped the warranty card!!