Hi Cap
firstly the Eynsham Marina isn't in Eynsham! It's about a mile down the B4044 towards Oxford at the edge of a village called Farmoor.
If you look at a map of the area, you will see that the Thames does about a 90 degree turn at Farmoor and nearly touches the B4044. That's where you'll find the marina.
About 1/2 mile downstream from the marina (in the general direction of Eynsham) there's a toll bridge & lock at Swinford, which consists of about 3 houses and a pub. I can't remember its name, and have never been in it, bit WTH it's a pub. Park the boat near the lock and walk about 400 metres towards Eynsham & you'll find it.
There are more pubs in Eynsham but nothing in Farmoor
have a good one.