When you remortgage to HSBC with additional borrowing

IAMIAM

Do they open up two separate accounts, if the incoming mortgage has two accounts, or will they combine?
If you remortgage to HSBC and want additional borrowing from them, do they open another account or do they just open one with the amount you want?

[Deleted User]

They have 1 account for the current balance of the current mortgage and then a seperate one for additional borrowing.   
They do exact like for like remortgages so if you apply for £150,000 and the solicitor reports your balance on redemption to be £149,870 then they only release £149,870.  
They then have a separate account for additional borrowing.    All funds get released at the same time and a single payment comes out but internally they have 2 accounts.