The most important thing to remember re: Mortgage Repayment Protection (the optional one) is that if you opt not to take it, you CANNOT ask for it later, without re-mortgaging.
It is for that reason that the bank covers itself by asking you to formally decline the cover.
Took out mortgage in late 2000, took no cover at the time, downturn came, looked for cover, could not get it, made redundant and 'lost' 10k because of the lack of cover. I would not think twice about taking it up next time, but that's just me.