The main drawback with high loan to value buy to let mortgages is their are much fewer lenders, and the lenders around have slightly higher rates and fees.
But if you property has a good rental income it will allow you to buy the property with the minimum of cash down and increase the size of your portfolio. Interest rates are currently very low and should stay low for the foreseeable future. The Bank of England might start to increase rates a little bit at a very slow pace, but if they do, its likely as a result of the UK economy improving. In that case the rents will likely rise.
When you have a portfolio of properties with one lender, some of which have a very low loan to value, the lender may have an open facility with the borrower where they have an open line of credit where they can buy properties with 100% loan to value.
Lenders in our panel: