I didn't do enough research before I bought my train ticket from London to Edinburgh to leave at 11am. My flight arrives in London at 8am and from what I'm reading, customs can take an hour and going by underground takes an hour and I can probably expect an hour delay getting on the ground in London. I only have a carry on I'm bringing so that may help. Is 3 hours enough to make it or should I try and push my train ticket back?