Heatwave part 1: railway speed restrictions

We've been enjoying the most amazing spell of weather for the far north of England but trains in the Carlisle area have been experiencing speed restrictions because the line have been warped by the heat. I have always understood that they leave expansion gaps between rails to cope with the expansion of metal in warm weather. This is why trains traditionally go clickety-clack. But it appears that there has been some warping between the joints, hence the speed restrictions. But they have also been painting the rails white in places to reduce the absorption of infra-red from the Sun. I found https://www.networkrail.co.uk/running-the-railway/looking-after-the-railway/delays-explained/buckled-rail/ This suggests that modern rails are made from different bits welded together. I'm wondering if that means the expansions work against each other. Needs some research.