Hi Carmel,
Agree that most people will not be cost neutral as part of the switching process, due to the actual costs of switching. However, I do think you have to look at how soon the payback would be. If you benefit 70 euro a month on mortgage repayments, then you have a pretty good return for your 30 euro investment within 6 months !
And yes, it may impact a customers cash flow - this is always a possibility