Has anyone ported a mortgage to a much cheaper property?

[HangryFinch]

House worth £950k
outstanding mortgage of £630k
want to move to a house worth £715k

how would this work? Can someone explain like I’m 5. The mortgage amount. Needed would be less?

do you keep the rate? We are on 5 year fixed on a 0.81% deal with just under 2 years left (yes we were VERY lucky) want to avoid a hefty early repayment fee.

I might be talking bollocks but surely if you port, the mortgage will be the same? If you want to borrow less you’d have to remortgage and use some of your capital to pay off a chunk. And then I suspect there would be an interest penalty and/or early repayment charge.