If you are a member of the Big I in your state they can tell you which MGA will do that risk. Maybe if they are with Lloyds they might have claims and just got non renewed and had to get Lloyd.
No claims, I think the size is what did it. The premium for this is about 11k. Could be Lloyds was the only one the previous agency had willing to touch it, but it doesn't mean that is the only one that WILL touch it.