Request: Cryptocotyle lingua egg source

[DARWIN PC3]

Dear all,
I am a Masters student at the University of Sunderland (UK) studying 
parasites of the edible periwinkle (Littorina littorea).  I would like 
to do some work using the eggs of Cryptocotyle lingua, however, I 
cannot obtain any eggs.  I have tried to obtain them from Herring Gull 
(Larus argentatus)guano but this proved unsuccessful.  Does anyone know 
where I could obtain these eggs?

Many thanks in advance

John Knowles
email:es0jkn at environment.sunderland.ac.uk