The FSA have an establishment called "Fairlop Waters with Bar & Marquee", which doesn't have to be the name used on OSM, is that this location?

Fairlop Waters Country Park
Forest Road
Hainault
IG6 3HN

https://ratings.food.gov.uk/business/443095/fairlop-waters-with-bar-marquee

Also the Restaurant has the tag cuisine=greek , is that still the case? going by both your replies it seems the building should be tagged as

building=yes
name=The Boathouse
amenity=restaurant
bar=yes

with possible tags:
fhrs:id=443095
cuisine=greek