what sort of trade goods would you expect to see in the holds of ships crossing the English channel in 1115? would it vary much depending on whether the ship was going to or from the mainland?

Trade goods were different in both directions.

England exported wool, tin, meat, cattle and fish, and sometimes corn (corn only if a Royal licence was granted).

England imported wine, salt, cloth (at least finer cloth, from the low Countries, England was also importing woad, which indicates that England was weaving cloth as well even this early), silver, and exotic spices.

Passengers were also carried in both directions across the channel, mostly the Anglo-Normans who had lands and affairs on both sides.

https://books.google.com/books?id=HwUHBwAAQBAJ&pg=PA341&lpg=PA341&dq=Trade+between+england+and+France+in+12th+century&source=bl&ots=maT9FnBJeW&sig=XMS9wAc9WWkRY4mRIuHYjVYiFmw&hl=en&sa=X&ved=0CEoQ6AEwCGoVChMIuJ_N0J3tyAIVAR4eCh2H-gZy#v=onepage&q=Trade%20between%20england%20and%20France%20in%2012th%20century&f=false