Applying for a second mortgage with a different bank What information will they have on me?

In 2009 I bought a house with a first time buyers mortgage, but i decided to stay with my girlfriend in her own house and rent mine out. I redirected the mail from my house to my girlfriends address I'm also registered on the electrol voters role at her address all my bank cards are registered to her address as well drivers license, passport etc

I'm now interested in getting a buy to let mortgage on a different property, if the bank asks me where i live should i say at my girlfriend address or at the address that i have the first time buyers mortgage at.

Also can they find out what kind of mortgage you have on your credit report

Cheers

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