If ones investment journey is well spaced, I cannot see a problem with online cheapies. Just refinance to a suitable lender whenever you are ready with IP1/2/3. The admin costs will probably need to be lesser than the savings one made off an online cheapie. Atm, I am not experienced with this, but doesn't look too bad to me. What could go wrong with this approach ?
Online lenders usually have a fairly conservative calculator, so investors on average incomes with more than a couple of investment properties arent going to be able to switch to an online lender easily.