It sounds like you already have a Realtor. Do they have a CIPS designation? Or another continuing education certification that suggests that they specialize in International transacations?
This is certainly not required, but I've found that agents with this or similar designations tend to have a bit more expertise with transactions involving either International clients or properties.
If your agent does not have this designation, then you might want to ask them if any other agents in their brokerage do have it. But I am not suggesting that you try to change agents.
If your agent is or locates an agent with this specialty certification, then they might have more specific experience with lenders who can help you price compete your loan. In this particular interest rate environment (at least in the U.S.) 30% down does sound a bit high. But I don't yet specialize in International real estate or mortgage services, so I would not know if you can get more favorable terms at this point in time.
I could suggest some lenders that you may want to speak with, but I'm also not sure of their specific experience with respect to International clients. However they are all very good lenders and if they could not assist you would be happy to refer you to someone who could.
Good luck and let me know if I could be of further assistance.
Broker Associate, Sudler Sotheby's International Realty