Dannyboy to Mother Goose, package delivered.
PM me your paypal and I'll sort out the postage cost.
Over and Out.
*****
The rear shock is a Marin branded Shockworks MonoShock and looks not dissimilar to the type found on a Tesco bike

. I have the spring tension to play with but nothing else I can see.
I did a bit more research on the Marin Shoreline trail - it was a pretty low spec bike so the rear shock makes sense and the forks I have put on (a very budget rockshock) are a bit of an upgrade over the originals.