Owning your own home

With repayment you will be paying progressively less interest, so the interest you gain on the ISA is cancelled out. As the banks have to make money the rate of interest they charge you is always going to be more than they pay you.

It's a interesting idea, but I wouldn't do it.

That's true if you go for a fixed interest ISA.
You might invest in, christ knows what, Gold or something, within your ISA and make MORE than whatever your mortgage interest rate is.
Then you are better off.

For example the compounding effect of good returns on my investments in my ISA have far outweighed the paltry 2-3% or whatever it is that I would have achieved if I just paid down my mortgage so I am far better off having the ISA vs. a repayment mortgage.
(Even including the disastrous Aug+Sept stock market...)