This was done via an automation on the bank's website tonight. I have a large deposit and would only need to borrow about £50,000.
I was refused a mortgage in principle, quite shocked. I checked my credit score, which is fair and a few points off good. Apparently my negative points were - wait for it - not having a mortgage!! - and not having a lot money in my credit account (I have quite a large sum in my account so I cant imagine what they mean).
After speaking to a mortgage advisor they thought I'd be offered one quite easily from the bank. Now what?