I think they are both saying the same. tali.
If you have a Repayment mortgage of, say, �60.000 over 25 years, your Capital repayment each month will be this figure divided by 25 (years) and then by 12 (months). ie �200 per month. (200 x 12 x 25 = 60,000). On top of this, you will, of course, pay interest at the current / agreed rate on the outstanding amount. This means you pay interest on the full �60,000 at the start of the loan, on only �30,000 about half-way through, and minimal amount just before you pay it off.
With an "Interest Only" mortgage, it is just that. You pay (in the above example), interest on the full �60,000 for the full 25 year term of the loan. In the meantime, the Lender (bank / building society) will expect you to have a "vehicle" (an investment of some kind) to pay off the capital at the end of the term. (This would normally be some sort of stock market based investment that would offer returns better than that of a savings account etc. - but also higher risks, hence the hoo-hah over 'Endowments')
If you switched Loan type mid-way through the life of your mortgage - eg. from "Interest Only" to "Repayment", the lender will (should !! ) take into account the actual / prospective value of any previous investment or 'Repayment Vehicle" before re-calculating, rather than expecting you to repay the whole capital (plus interest) in just ten or so years.
Hence, Ethel, dzug and zork are all basically saying the same thing.
(Psst - hope all goes well !!)