I knew there was a trick to this. I know what I'm doing next time. Thanks.
I've only just heard of this piece of card trick, and I'm going to give it a try, but having practised loading film straight on, I'm now fairly confident I can get the (120) film on the spool without any buckle marks every time. Sometimes it still takes a few attempts to get it started, but I'm getting better!. With a bit of practise you don't need bits of cardboard. 35mm is a doddle. Mind you, never tried a changing bag - it's much easier in a darkroom (except when you drop the film and it rolls away. Amazing how big a small darkroom can get when you are doing a fingertip search to find the pesky thing)