Hmmm...depends where you are, I know of a few in Epworth and Westwoodside, the yard where I am at is based in Westwoodside and there are two spaces open at the moment if that's any good for you? Just ask if you want more details
You could try the military base in kirton in linsey, they used to take liveries not sure if they still do. Nice big indoor school too. Last time i drove by i could see horses out so worth a try. It would be diy though as it is no longer a saddle club since the Army left i believe.
Just another thought, have you tried the notice board at Thomas Bells in Brigg? It is normally packed with ads there for the smaller yards in our area.