The only advice I can give is check the labels.I now only have real butter, avoid any products which only say veg oil on the ingredients unless I have checked with the company thats makes them.
I'd be careful about doing this. The reason that companies use vegetable oil on labels is to allow them to switch oils if they find something cheaper, so just because they're using something other than rapeseed/canola now, doesn't mean they won't switch to it in the future.
I found some information saying that rape seed is fed to cattle, chickens and pigs.. does some meats affect you if they have been fed rape seed?
I'd expect that what they are feeding to cattle is what's left of the seed after they've extracted the oil. Also, whatever the animal eats is digested by them, which means that it is broken down, so I'd expect that you are pretty safe.
Is this something that will be put on the packaging as well?
I can't see that happening. You would need to buy your meat where you can identify the source if you wanted to be able to check this.