Which bank or building society is giving the highest loan to income ratio (How much can I borrow) for residential Mortgages?

Its a minefield, and most have a max mortgage and max debt cap.

Generally a 10% deposit and at least £25,000 income is required for a 100,000 buy to let. (RBS)

AND the buy to let will require a monthly minimal rent of £521. (You can charge what you like above that, but the bank actually set in terms the minimal rent u can charge to cover mortgage upto 30 years or you die whichever comes first.

I have 18m worth of property and most fully owned - i cant get a mortgage over 5m (Morgan Stanley business mortgages over 10 years at 4.3% interest.)

To own your own home, you would need 3x your annual income. Total you can borrow. (most banks)

With deposit "some" banks might go as far as 5x your annual income (20% deposit generally but not always)

All mortgage lenders use the same formula in determining a potential borrower's debt ratio.

The mortgage loan program would depend on the how high your debt ratio could be in order to be approved for a mortgage loan that would determine the amount a mortgage lender would be able to lend you.

Most mortgage lenders have the same mortgage loan investors that set the guidelines as to what is necessary or needed to be approved for a mortgage loan approval.

No mortgage loan lender has a special mortgage loan investor that do business only with them. These

mortgage loan investors would want to fund as many mortgage loans as possible, therefore they do business with most all mortgage lenders.

When speaking with your loan officer and underwriter they would figure out your debt to income ratio and find a mortgage loan program that you would be approved for. If one mortgage loan investor have guidelines that would approve a mortgage loan for a potential borrower with a 45% debt to income ratio and your debt ratio is 42, this is the mortgage loan investor your underwriter would select for you.

I hope this has been of some benefit to you, good luck.

"FIGHT ON"

you will have to call several banks and find out what they use