Ian & Hilda Dedic gurgled happily, sounding
much like they were saying:

Next doors owners want to cut the pillars which support the breezeblock
walls back to flush with the outside of our garage (there are 4 pillars
about 6ft apart along the outside wall of our garage so the inside of
our garage has flush walls).

I believe that cutting these pillars will weaken the wall structure and
make the garage fall down.

I need a quick answer on this as I need to persuade him he can't do this
in the morning.

It's quite simple. Unless and until his architect can show you structural
calculations to prove that it won't, then all bets are off.